1 [caption]: Monterey Bay Aquarium, south of San Francisco...
1 Jamie: Here's the shark, in this tank.
2 Steve: Crikey! 'e doesn't look stroppy enough to me! All this easy aquarium food's made 'im soft!
3 Adam: Shall we get a different shark?
3 Steve: Nah, I'll sort 'im out!
4 [sound]: Splash!
4 Terry: Steve! No!!

When I planned this sequence, I originally wanted to use the same aquarium that Kirk and Spock rescued the whale from in Star Trek IV: The Voyage Home, which was apparently somewhere in suburban San Francisco, just a short bus ride from where they parked their captured Klingon Bird of Prey in Golden Gate Park. Doing the research to discover what that aquarium was led me to the discovery that the "Cetacean Institute" was wholly fictional, and scenes there were actually filmed at Monterey Bay Aquarium, some 200 kilometres south of San Francisco.

Which I thought was pretty cool, since I have actually visited the Monterey Bay Aquarium myself. If you get a chance, it's definitely worth a visit.

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2015-03-04 Rerun commentary: I went with a layer of solid blue bricks to represent the surface of the water in the shark tank. This necessitated pulling up some bricks to leave gaps where I could place other objects, such as the shark and Steve. I also left a brick at an angle to crudely simulate a splash.

Another option would have been to use a lot of very small LEGO bricks, such as 1×1 circular plates, possibly in the transparent blue colour, and just jumbled loosely together (as opposed to built together). I've seen this done on other LEGO sites, and the effect is very good. The main problem for me was I didn't have nearly enough 1×1 blue circular plates.