content: dont worry, it probably isnt.  how these whales hunt the krill they eat is by blowing bubbles in a big circle to corral the krill into a ball.  the whales then come up from the bottom and take a gulp of dinner.  since they're baleen whales, theyll use their tongues to push the water out and keep the krill in using those "teeth"  more like a natural broom in their mouths.  so basically the dude in the boat would have seen the bubbles, and should have known to GTFO