Hi, what is the difference between a cavern and a cave in the ocean – when scuba diving?

Do you need special skills for both?

I assume you are diving!

PADI cosider a cavern to be the area of an overhead environment that is still lit by natural light.
A cave requires lighting artificially.
Special training is required for either as you will be in an overhead environment with no direct access to the surface.

If you are interested in either, contact your local PADI school for Cavern or your local cave diving assoc.