Stupid is as stupid does. First, they boat out into an area suspected of venting methane, whereupon had they entered it, the principles of buoyancy allowing their craft to float would have resulted in their sinking. Of course if they didn’t sink, and there was methane there, then the odorless and colorless gas could have caused death by suffocation.
That's right! I forgot all about that. I read a fiction book that used this principle and explained how gas can actually sink big boats in a perfectly calm sea. I sort of forgot how...