1. My first thought was a rather silly “they can’t see the sky from under the water…” but like, they have to surface all the time, so they see the sky way more than most modern humans, and at regular intervals.

This does suggest a rather conscious plan of migration that is probably off-putting to people who aren’t comfortable with the idea that whales might be smart enough to do that.

4/5: Some might be able to see a lot of features with their sonar too, or the sound of the long reverb in different areas, like when they get to the deep trench, they get a more echoey effect.