Santa Cruz Island has some of the largest, and deepest sea caves in the world.
The largest is known as Painted Cave because of its colorful rock types, lichens, and algae. 
The entrance is 160 feet feet high, and the cave is nearly a quarter mile long and 100 feet wide.

 

This is a view from inside the cave looking out (from a two-story high boat).

An example of the colorful cave walls.