I think that's a Blue Whale. Freakin' huge !!
en.wikipedia.org/wiki/Blue_whaleThat dorsal fin is probably the same size as a dolphin's. Looks like it would have the same effect as a 1/2 inch fin on a 17 foot Down Wind Board !!
PS - someone dropped a red thumb, and I cancelled it.... paddler is keeping their distance.... that red thumb appeared personal!
I'll wait for my red thumb now !
