Sea Life is not the biggest aquarium so does not compare to any larger ones you may have visited.
However, it is still a great place to bring the kids for a couple of hours (and better value and a full day out if you buy a Combi ticket with Legoland Discovery next door).
There are plenty of tanks with fish, turtles, stingray's and sharks to see as well as an interactive touch pool which the kids will love. The kids will have great fun in the play area too and as it is so compact the parents can relax while the children run around.
There is an attraction called SeaTrek where anyone over 8 can walk in a large tank with a divers mask and wetsuit. It is expensive but looks like it would be a great experience.