International Water Ski Federation
Environmental Handbook for Towed Water Sports



Like most human activities, water skiing causes a certain degree of impact to the natural environment in which it takes place.  Whether that impact is negative, neutral or potentially even positive is often a matter of some debate.  Studies and reports rarely come to the same conclusions concerning either the degree of impact or the relative priority of any one issue as opposed to another.  Several major studies undertaken in Europe and the United States conclude that in general, and relative to other boating activities, water skiing does not significantly impact the natural environment.  On the other hand, various studies and one book in particular conclude that boating (more so than water skiing) does have a significant ecological impact, particularly in regards to certain environmental issues. 

Rather than enter into this ongoing debate, the following pages focus instead on the most commonly cited and studied environmental impacts associated with boating and water skiing, drawn from the literature review.  

The objectives of this section are to provide the reader a description of what impacts are associated with boating and water skiing, and secondly, how these impacts affect the environment as well as human, animal and plant life. 


What would water skiing be without water, moreover, without CLEAN water? 

We are all globally connected through nature’s ecological cycles, in particular the water cycle, also known as the hydrological cycle. Through a variety of unique natural processes all of earth’s water supplies, be they from rivers, icecaps, oceans or seas, eventually evaporate into the atmosphere to become part of a continuous phenomenon called the hydrological cycle. Those raindrops that cause you to cancel a day of water skiing are actually part of a much larger and vital natural process, one that all living beings depend on for survival. 

When unnatural substances, like hydrocarbon emissions from the burning of fossil fuels, enter the hydrological cycle they have a detrimental effect on earth’s ecosystems, and human health.  This is evident from the damage created by acid rain and greenhouse gases which are the products of human activity.

Acid rain is precipitation that contains a high level of acidic compounds such as sulfur dioxide and nitrogen oxide which come from fossil fuel emissions and some natural processes like volcanism.  These compounds react in the atmosphere to produce sulfuric acid, a highly corrosive compound, and ozone, a major factor in the trapping of heat and pollutants close to ground level – the greenhouse effect.

Greenhouse gases related to human activity are increasing at an unprecedented rate leading to an overall warming of the earth’s surface, called the greenhouse effect or global warming.  The principal gases related to human activity include:

Carbon Dioxide (CO2) -- the major contributor to the greenhouse effect primarily from the burning of fossil fuel, coal, oil, gasoline, and natural gas

Methane – from natural decompostion process involving bacteria and the absence of oxygen -- considered to be about 20 times more powerful as a greenhouse gas than CO2

Nitrous Oxide (NOx) -- from burning of fossil fuels, nitrogen based fertilizers, and some man-made chemicals such as nitric acid

Ozone – main component of urban smog caused when volatile organic compounds (VOCs) and N0x react with sunlight. VOCs are released from a wide variety of chemicals and solvents

Halocarbons – they trap heat in the atmosphere much better than CO2 – the best known of these is chlorofluorocarbons (CFC) which is known to destroy the ozone layer. The ozone layer protects us from ultraviolet rays that can cause melanoma type cancer and cataracts.



The main environmental impacts associated with boating and water skiing fall into four key categories:

  1. Noise – engine and human noise

  2. Pollution – chemicals, gases, solid wastes, and biological contamination

  3. Geomorphology and Hydrology – shoreline and flora degradation, and turbidity

  4. Birds and Wildlife – disturbance and dislocation

Some of the more common types of impacts associated with these categories include: 

While most of the above impacts are negative, there are also some benefits of both water skiing and boating on the environment.  

BENEFITS of Water Skiing and Boating on the Aquatic Environment

In some instances, boating and water skiing can directly benefit the ecosystem by adding much needed oxygen to the water body.  Studies have indicated that the action of the engine propeller, the boat hull, and the water skier cause an increase in the oxygen content in the water.  This in turn can benefit the health and diversity of the animal and plant life living in that water.  This oxygenation process is most advantageous in shallow waters, waters that have minimal fresh water exchange and a high incidence of algae growth. 

Another benefit of water skiing and boating is the removal of carbon dioxide, and other pollutants, from the water body.  This benefit is credited to marine engines with underwater exhausts.  As the bubbles containing the exhaust gases are dispersed behind the boat they help to reduce noise and to transport emissions to the surface where they are evaporated.  An underwater study done by Outboard Marine Corporation found that air bubbles moving through the water at high speeds can help to degrade certain pollutants. 

In narrow waterways, especially canals, a low density of regular boat traffic discourages the overgrowth of potentially troublesome plant species, and helps maintain a diversity of native plant species.  In addition, the restoration of disused canals and open pit mining quarries for water based recreation has benefited many types of wildlife and waterfowl. 

Furthermore, in some cases the presence of water skiing has led to significant enhancements to the local ecosystems.  In one region of the United Kingdom, a local water ski club, together with the region’s conservation authority implemented a comprehensive remediation strategy to protect both plants and animals along a stretch of river.  Some of the actions taken included the introduction of native plant species, the construction of natural berms and islands, the implementation of strict no-pass zones along certain shorelines, and the creation of a slalom course a safe distance from nesting areas. The enhancements would most likely not have taken place if the water ski club had not initiated them. 


When compared with many other types of human activities, water skiing is not particularly noisy.  The typical, older two-stroke, 68 horsepower engine, operating under normal water skiing conditions produces a range between 60 to 70 dBAs[1].  

The following values help put this range into perspective relative to other types of common noise pollution: 

·         120 dB(A)        Discotheque – 1m in front of loudspeaker

·         100                 Pneumatic drill at 5 m

·          70                  Telephone ringing at 2m

·          40                  Refrigerator humming at 2m

Unfortunately, in many parts of the world water skiing still has a reputation for being a noisy and dangerous sport, often more so than other watercraft activities.  Recent studies on engine noise undertaken in different countries have shown that the typical water ski boat engine produces a level of noise well below the national standards for noise, and frequently below that of other watercraft. 

In recent years, marine engine manufacturers have taken significant steps to reduce the level of noise created by their motors (refer to Appendix B on Marine Engines for more details).  This move towards quieter technology should help to counter the image that water skiing and boating are excessively noisy. 

BWSF’s Code of Practice for Noise:

The British Water Ski Federation has produced one of the most thorough and widely used documents on noise entitled  “Code of Practice for Water Skiing & Noise” (1997).   

Table 1 reveals the BWSF’s standards for noise emissions for water skiing:

Table 1British Water Ski Federation’s Standards for Noise

Maximum noise emission for one recreational boat:
75 dB (A) for boat traveling 22 miles per hour at a minimum of 25 metres from shore  

Maximum noise emission for any boat traveling outside an environmentally sensitive area:

55 dB(A) Maximum noise emission for one boat for water ski racing (other conditions stated in Code):
98 dB(A) with boat traveling at constant maximum design engine speed, 30m from shore
105 dB(A) for international and World Championship IWSF sanctioned events

[1] dB(A) – dB stands for decibel, which is a logarithmic scale used to measure sound. ‘A’ means it is a weighted decibel which is an internationally accepted unit for most noise measurement, and represents the sound pressure level weighted to correspond to the frequency response of the human ear.

It is important to remember that noise is a SUBJECTIVE, and SENSITIVE issue -- what is offensive to some may not be so to others.  It is wise to approach all conflicts related to noise disturbance with sensitivity.  Always respect others’ right to peaceful enjoyment of their property and common waterway. 

A recent trend of concern is the increase in boat and jet ski stereo systems with large amplifiers. As sound travels much farther on water, skiers and boaters should make sure to keep the volume low and respect other’s privacy when on the water. This additional source of noise could be a detriment to the image of boating and water skiing if allowed to get out of hand. 

It is responsible boating to always abide by the club/marina’s Code of Practice for Noise.  If your club/marina does not have a Code, a copy of the BWSF’s can be obtained and customized for your club/marina.

2.  POLLUTION – Chemicals, Gases, Solid Waste, and Biological Contamination


Despite the best efforts of responsible boaters to prevent water contamination, gasoline and oil exhaust, namely hydrocarbons, are released every time a marine engine operates.   Depending on the type of engine used, the degree of such pollution will vary. 

Have you ever wondered what a few hours of boating fun and water skiing activity may be doing to the water we swim in and the air we breathe?

On an individual basis the impact of your boat and skier on local ecosystems is minimal. However, over time, and considering the combined effect of thousands of other boaters and water skiers around the world, the impact can be significant. 

Consider what the typical marine engine emits from a few hours of water skiing activity. 

 A Typical Two-Stroke Boat Engine and its Emissions: 

The impact of a two-stroke, 68 horsepower outboard (built before 1997) mounted on a 17 to 21 foot planing runabout boat hull -- at the lower end of boats commonly used by recreational water skiers -- serves as a useful illustration. 

During a three to four hour afternoon of water ski and boating activity this two-stroke engine will consume about: 
      20 gallons (80 litres) of gasoline and
     3.5 pints (2 litres) of lubricating oil.

 Of this, approximately 30 percent of the "unbent" (see Table 2) gasoline will be emitted directly into the water during operation. 

Estimates for the United States alone are that  567 million to 1.6 billion litres of unburned fuel is exhausted into the environment each year by 12 million gasoline powered pleasure boats (1993 figures). 

SO, What’s in Boat Engine Exhaust?

Table 2
Boat Engine Exhaust

Emissions from two- and four-stroke gasoline and diesel engines includes:

  Unbent or partially burned fuel molecules that react in the atmosphere to form ground-level ozone, a major component of smog.  Some hydrocarbons, such as benzene, are toxic and may cause cancer or other health problems.  Another source of hydrocarbon pollution is fuel evaporation, which occurs when gasoline vapours are forced out of the fuel tank (during refueling) or when gasoline spills and evaporates.

An exhaust product that comes mainly from diesel-fuelled vehicles.  These microscopic airborne particles can damage the respiratory system and contribute to nuisance smoke and odour associated with diesel exhaust.

Nitrogen Oxides:
Nitrogen and oxygen in the air, when subjected to the high temperatures and high-pressure conditions in an internal combustion engine, form nitrogen oxides.  Nitrogen oxides react  in the atmosphere to form ground-level ozone and contribute to acid rain.

Carbon Monoxide: 
A colourless, odourless, poisonous gas that results from incomplete fuel combustion.

Carbon Dioxide:
  CO2 is the ultimate product of burning carbon-based fuel.  Carbon dioxide does not impair human health, but it is a “greenhouse gas” that contributes to the potential for global warming.  As engine fuel economy declines, carbon dioxide emissions increase.  

WHAT Happens to Boat Exhaust?

Hydrocarbons end up in the water column, in the bottom sediments, as surface film, or released into the atmosphere.  Atmospheric hydrocarbons are also a prime cause of greenhouse gases and thinning of the ozone layer.  Furthermore, both burnt and unburned fuel contain compounds, like polycyclic aromatic hydrocarbons, that are toxic to aquatic organisms and are linked to human illnesses like asthma, cancer, and genetic mutations. 

However, there is considerable evidence to indicate that marine engine exhaust does not cause permanent damage to the aquatic environment.  In particular, evidence of hydrocarbon accumulation in the sediment is inconclusive, and lead concentration is not thought to be significant.  It is therefore most likely that the majority of the exhaust emissions are ending up in the atmosphere, where they are quickly dispersed.  This may be good news for the local marine ecosystem but not for global air quality. 

SOLID Wastes 

All man-made materials abandoned either on land or in the water can be considered waste, or more commonly, garbage.  Not only is waste unsightly, it reduces the esthetic appeal of a club/marina and its grounds and waterways, and is a hazard to wildlife, birds and even children.  Some wastes, even though they are biodegradable, will persist for many years. Those wastes that are not made of natural materials will either break down and leach minute toxic elements into the soil and groundwater or they will persist for decades and even centuries. 

To sort, haul, and dispose of wastes costs the club/marina and governments considerable amounts of money that could be better spent for more productive purposes. 

Fortunately, wastes are one of the impacts that club/marina operators can address through a waste prevention plan and Codes of Conduct (addressed in Part D). 

Individuals also play an important role in the success of the waste prevention plan.  Part C offers several suggestions on ways individual water skiers and boaters can prevent wastes, and dispose of them properly. 

BIOLOGICAL Contamination 

Biological contamination is a term used to describe unwanted, non-native organisms, both plant and animal, that can invade aquatic ecosystems. Water skiers can unwittingly play a role in spreading these species when boats and watercraft move from one water system to another without taking proper precautions to cleanse themselves of these unwanted "hitchhikers". 

The zebra mussel is one such organism that has wreaked havoc in many water systems throughout North America.  The mussels attach themselves to boat hulls and propellers, intake and outtake valves, and water ballast tanks and spread rapidly once relocated to a new body of water.   The plant contaminants, such as hydrilla, hyacinth and milfoil, can spread in a similar manner as the zebra mussels. 

These organisms also cause an increase in fuel consumption, a decrease in native plant diversity and survival rates, deoxygenation of the water body, loss of fish life and other aquatic species.  They can also prevent the safe use of a body of water for recreational activities like water skiing or swimming as the water becomes so clogged as to be impassable.  Many of these biological contaminants are difficult and costly to remove. 

For additional information on the different categories of pollutants, their harmful effects, and points of control both on and off the water please refer to Appendix A. 


SHORELINE Degradation and Turbidity: 

Shoreline erosion, degradation of shoreline flora, and turbid water (unclear or sediment-filled) are natural phenomena resulting from wind action and hydrological activities.  They are also directly affected by human, water-based activities such as boating, water skiing, and docking. 

Compared to all factors, such as weather and other watercrafts, recreational boating activity has been shown to contribute minimally to erosion and turbidity.  However, some studies have shown that if water skiing and boating are practised too close to shore, and in environmentally sensitive areas, the impact from boat and skier wash can be significant. 

Determining the degree of impact is complex and often involves any combination of factors from the number of boats, to the shape of the boat hull, to the speed of the boat, to the depth of the water, and the distance the boat is from shore.  

When considering the causes of erosion and turbidity both natural phenomena and seasonality must be taken into account.  Wind action is a major contributor to both and has a greater impact during the winter season when weather conditions can be a great deal rougher.  Other factors that will influence erosion and turbidity include the form and composition of the soil, the shoreline gradient, and the degree of natural or artificial protection.  The degree of damage can be severe at sites which have unstable soils, or generally weak vegetative growth. 

Turbidity is caused when engine propellers and boat wash stir up bottom sediments in shallow waters and the particulates remain suspended in the water column.   The degree of turbidity is directly proportional to the depth of the water, i.e. the shallower the water the greater the turbidity levels.  

BIRDS and WILDLIFE – Disturbance and Dislocation: 

Considerable research has been undertaken in different countries to determine if and how boating and water skiing affects birds, namely waterfowl.  Considerably less work has been done on the impacts on wildlife. 

In general, the majority of boating and ski activity that takes place 50 metres or more from shore usually does not cause any significant impact to birds and wildlife.  However, where the disturbance and dislocation is often the most serious is: 

Birds, particularly waterfowl, nest close to shorelines and are especially vulnerable when  molting (losing feathers).  As each water body will have different characteristics related to types of species, nesting habits, and seasonal factors, it is difficult to generalize on the impacts.  However, what is known is that in areas where waterfowl disturbance has been recorded, the types of impacts can include relocation of nesting site, abandonment of nest, and loss of young.  There can also be long term impacts as many species of birds that normally would return year after year to the same nesting area are forced elsewhere to perhaps less desirable bodies of water. 

In general, measures to protect waterfowl are also beneficial in protecting wildlife. 

In summary, it can be said that all of us have a responsibility to ski and boat with care and to show respect for the environment and all the living things in it. 

With that goal in mind a universal motto for the water ski community could be:

Back to Index

Introduction - Part A


Practical Steps to Environmentally Responsible Water Skiing and Boating - Part C

Recommended Best Practices for Club/Marina Operators - Part D