Did the Walrus & Beluga tour in Feb. It was really good. You get to see the behind the scenes walrus area, and feed a fish to the large walrus "Garfield." The trainer answers questions for you. Then we went to a room with mirrored glass, where we could see the young walrus' they had there. They are not out in public view yet (may have changed since Feb though). We went to the behind the scenes beluga area as well, and each person/group got to go one on one with a trainer to ask a few behaviors of a beluga and toss a few fish. They were working with acclimating the belugas and the harbor seals in the same exhibit while we were there, so it was cool to see that interaction. While each group was waiting to go up to the belugas (there were a few belugas, so it was 2-3 groups at once), the waiting people were able to pose more questions to the trainers.
Even though we got half price tix via a black friday deal, there were not too many people on the tour - about 12 total. As noted above, they do provide you a locker as you cannot bring cameras / etc. on the tour.