I did a lot of driving around the marshes, bayous, and inter-coastal waters down in Louisiana on a freakin' airboat. The ones that I was riding around in have big v8s (like 400+ ci engines, none that were familiar to me though) and open headers. Although they're great ATVs of a sort, they have their downsides......they're WICKED Fn loud for one thing!!!! They're usually fine in backwaters and bayous but open water can be sktechy. Any wind and you're not going over open water. Also, the hulls of the ones that I was on were modified and reinforced with thick aluminum plates.