Hi OP!
We have done this twice. I was just talking about it yesterday. Odds are VERY GOOD, if I end up on any Nassau cruises, I'll be going straight to Blue Lagoon EVEN if I didn't get an encounter. It's like paradise! Our first sea lion encounter was a bucket list! The second one a year later, they were having problems with one of the sea lions (one was recovering from an injury or illness and the others weren't as well trained) so we didn't get to get INTO the water with them, we just got to shake their flippers, take photos etc. It was slightly a bit of a let down, however, animals obviously take priority. It was a bummer because we had a whole new family with us that we had talked up the event, and they were just eh about it I think as a result. The family DID say they liked it way way way better than Atlantis and would consider another cruise just to back to BL, which I totally get! Its got something for everyone and is exclusive so no riff raff. (Other than the other guests, ahem, chair hog people!)
If anyone has gone this year, I would ask which sea lions they saw. We had Maggie and Bonnie the first year, and it was amazing. I would love to see those sweet girls again. We still loved it, but it wasn't AS good as the first time.
Also, for dolphin lovers, their push excursion is definitely one of the best I've seen. We just sit there and watch them. Judging by their expressions, it is definitely bucket list material for these guests.
LOVE BL! Dont' forget to order the conch fritters whatever you do!