On some houseboats carbon monoxide can accumulate under the swim platform
The National Park Service continues to stress the dangers of carbon monoxide (CO) and boats. This is an odorless, tasteless gas, which can kill you. The gas replaces the oxygen in your lungs and if you do not receive oxygen soon, the damage may be fatal. While past emphasis has been on houseboats, studies show that all boats can collect dangerous levels of CO. Anytime generators and/or engines are running, CO is produced. Do not allow passengers to congregate around engines or the backs of boats when engines or generators are running. This is especially important when you may enclose the boat for warmth. For some boats, which vent CO out the back, this deadly gas can collect under the swim step and spaces under the boat. The CO remains there long after engines and generators have been shut down. Don't play or swim under the swim step or under the boat. Use carbon monoxide detectors. Always be aware of the dangers of CO around your boat.