I can't provide a peer reviewed scientific study that the whales are not that stressed by human but I don't see any one (peer reviewed also) saying the whales are stressed and I don't really believe they dive deeper for those tiny animals, us, on the surface. The calves are not stressed that's for sure. They are very curious and come to see the divers (and their mothers don't interfere on that) and are quite eager to play. I think quite a lot of wild species realize we are not a threat anymore and don't mind us a lot. As I said before, those whales have seen us since they were calves and saw we don't do anything to them. We are part of their environment as birds are for us. That doesn't mean we should do anything and not try to respect other animals...