Don't bet too hard on them not being a prey item. In '88 I saw a full grown bull Sea Lion get hit at the Farallons. It did a double back flip with a total height of over 12'. That was an Awesome display of force! Nothing else happened for about 20-25 minutes, then in 7 shots from atleast 2 different sharks it was gone in less than an hour. All that was left was a huge pinkish area in the water. Kind of strange was that the fishing turned on when it was all done. Never seen so many big lings in 1 trip. 15 over 15# were caught in 2 hours.
Tight lines,
Wade