deep sea diving...

Well, we were on a mission to find or retrieve an item from the depths of a large body of water. The means by which we traveled was this enormous llama like sea creature. Three people were riding on it's back as it swam deeper and deeper, but with each length would rise back up to the surface for air, for everyone. So I'm not really sure how it kept getting deeper if it had to get air again and again. Lots of other things happened.