There is one cave I really like, and that is the Sea Lion Cave, near Florence Oregon...we have been there a few times...you have to take an elevator several stories down to get to the bottom of the cave...
When you get down there, you can see where the ocean washes into the cave...in late Jan. and Feb, the sea lions come in there to have their babies...there are sea lions there year round, but birthing time brings hordes of sea lions...I swear when I was there, there were thousands and thousands of sea lions in the cave...the sound of all those sea lions was deafening, and it was really a sight to see...