I'd have to do a search...which you can do as easily...it has been published that the northern islands were never connected to the mainland....I think that the part between Anacapa Island and the Santa Monica mountains has subsided over the last 1 million years ago so was more shallow in the past....but if it was connected in the last million years you might expect species to be on the islands that are not. I've seen artifacts in area of one of the landslide...you just leave them along. there was a high population of native americans...so there are sites all over. There are very large sea caves on the north side of Santa Cruz Island. One is called "blimp hanger" because it is so large you could park a blimp in it. A better known cave is Painted Cave...I've been in it twice on 70 foot boats...a kayak can get back farther...maybe 200 or 300 m
Daisy Cave on San Miguel Island has evidence for some of the earliest people of North America...about 15,000 years...they had to get out there by boat....
Chris