Float flying in Canada (west coast). We were going into a logging camp, small inlet amongst serious mountains, so a pretty constrained approach to save miles of taxiing.
Short finals to the beach - up pops an otter! So a small head amongst a lot of sea, and still about 300m away. Instructor says - "its ok, he'll dive" and of course he did, once he spotted us.
The point is though that otters and swimmers are very easy to spot - so long as the waves do not obscure them for long periods. People are good at spotting patterns and pattern disruptions - something about once being hunter gathers.
Did he see the swimmers? I don't know - but then neither do the armchair critics. Equally during the same course - "never land in the middle of a lake" - if it goes wrong you'll die in the cold water. "If you have to ditch do it close to the shore" is the mantra for landplanes and simple survival is a pretty big motivator.
I'll never aim at swimmers - but getting close to them is a pretty good idea! They represent potential help and probably shallow water.