The effects boating has on the ocean:

http://epa.gov/owow/oceans/treasure/pg6.html

Although boating plays a large role in the U.S. economy, it can have harmful effects on the environment. Human waste largely contributes to the amount of pollution in the water and can lead to health problems and even beach closings. "The Vessel Sewage Discharge Program1requires EPA to regulate the discharge of vessel sewage by requiring most vessels to use marine sanitation devices (MSDs), commonly referred to as boat toilets, when operating in U.S. navigable and territorial waters."(EPA, Vessel Sewage Discharges: September 17, 1997. They also request "No Discharge Zones".