What do you do with the Sea Caves?

[hazy mountain]

I'm running through the Se Pulu Cave right for an entire day endlessly clearing trash in the caves. I'm lost, what do you with those caves anyway?

[gilded creek]

the cave is bassically just a place to collect trash and coffer. the type of coffer is based on which cave, cave at dua pulu would give the coffer type of that area, and so on

the cave is endless, sometimes the kelp spawn there too

[hazy mountain]

ah okay, I though the caves have something t do with the coral progression since I'm stuck at the area after the big ship at level 48m