Sea Life sits on the edge of Puerto Marina and is the standard branded aquarium experience: a long walk-through tunnel under a tropical-fish tank, a Mediterranean section with rays and small sharks, and the inevitable touch pool. It is well-presented, air-conditioned, and predictably popular with families on rainy mornings.
Tickets are noticeably cheaper if you book online a day in advance. Allow about an hour. The aquarium does some genuinely useful local work rehabilitating sea turtles, which is worth supporting.