How to get everything in Shoal Cave?

Question

I saw loads of shells and stuff on top of the stairs but I can't get them. Did Game Freak put them there to make people feel awful or I can actually get them?

Answer 1

You have to go into the Shoal Cave twice, once at high tide and once at low tide. Low tide will have no water, allowing you to get to the items on the lower parts. High tide will flood the cave, meaning you will need Surf to navigate.

High Tide is between 09:00-15:00 and 21:00-03:00.
Low Tide is between 03:00-09:00 and 15:00-21:00.

Serebii