I am doing this excursion in June...I will post my experiences when I get back!!
"Twenty years from now, you will be more disappointed by the things you didn't do than the ones you did. So throw off the bowlines. Sail away from the safe harbor. Catch the tradewinds in your sails. Explore, Dream, Discover."
My husband and I did this excursion in August of 2006. fish were rather non-descript, but the starfish were very colorful and the guides were quite good. And besides that, I don't know anybody else that can say they snorkeled in Alaska! Go for it!