Assuming that they are talking about a large whale and assuming that they are looking down at the ring of gas approaching them from below the surface and noticing what appears to be surface wave ripples outside of the ring...., maybe chunks of ice floating on the surface? Just how far off the water is the bow of this fella's boat?! He's got to be 70 or 80 feet off the water!
Hoax picture perhaps?
Whale hunters of WW2