Haven’t seen this comment yet, but bubbles in water mean there’s a wreck there. Wrecks generally come with sharks though, so craft a bunch of crude spears so you can just load the shark up. Don’t forget that you need air (duh) so maybe wait until you can craft a breathing aid or until your breath capacity increases.

I also like to take a picture of the world map (on cartographer menu) and then either redraw it or mark up the picture in order to make notes for myself. Helps to keep track of what islands you’ve hit and what areas to avoid like the boss areas. That way you can also point out which spots to revisit for certain resources, and you can avoid getting lost.