A little bit off topic, but not massively so. We have started our Christmas shopping and I thought it would be fun to find underwater / scuba themed gifts for the kids in our family and friendship circle. Here are my ideas so far, posted in ascending order of age.
It's a bit pricey, but this Finding Nemo baby swing seat does deliver a full underwater themed experience. One for the grand kids when we get them!
Then there's this toy aquarium from Fischer Price:
Still for the younger ones, after the success of Disney's finding Dory there are lots of fish figurines swimming around out there. I especially like Destiny the whale shark, available as a "swimming" plastic toy or a soft toy.
As the kids get older, you start to get a lot more options. The Lego City underwater explorer sets are pretty great.
Robotic fish are a pretty good option. This YouTube video compares the two most easily available makes: