Visiting all secret areas in Boku No Natsuyasumi 2

Except for the underwater cave in Ocean Area B where the Tyrannosaurus bottle cap is situated. Go and find that yourselves. :) (Transition to Ocean Area B swimming around the bend at Yohs (Rocket mans) house, then almost immediately dive after the transition in a gap at the very bottom on the wall there is the tunnel on your left-hand side.)