How do you get into the sealed chamber?

first go to pacifidlog town then go to your left the should be an ocean current go aliitle bit below the middle then let the current take you you WILL have to go on land about 3 times then there will be a dive spot semi protected with rocks(dont worry its east to get around) then use dive if your at the right place then there will be some brille it says to go up here the there the cave. good luck.