Raisis cave

Some info about sea caves:  Sea caves are formed by the power of the ocean attacking zones of weakness in coastal cliffs. The weak zone is sometimes a fault, or fractured zone formed during slippage, such as Raisis cave.

Another type of weak zone is in sedimentary rocks where a layer of softer rock is interbedded between harder layers.(see example)

Yet a third instance is along the contact zone between dissimilar types of rocks where one is weaker than the other. Typically this is a dike, or intrusive vein of more easily eroded rock found within a stronger host rock.

The cave may begin as a very narrow crack into which waves can penetrate and exert tremendous force, cracking the rock from within by both the weight of the water and by compression of air. Sand and rock carried by waves produce additional erosive power on the cave's walls.