I've been on a jet ski, seen a hundred or more people ride them and never saw anyone ever wear a helmet on one. lol Snowmobile I can see helmet but jet ski and a sitdown one at that. naw. Now maybe like pros that go 100mph or something but this looks like just a regular one. You fall into the water, the engine stops as soon as you fall in as well, pretty safe. Never see people water skiing with helmets either.