A new 6 marine life objects set found under Decor / Sculptures, all cost 0. You need Ambitions ( or a later pack ) for the marine life objects to show up in your game. Use cheat moveobjects on to place items. Also use the cheat disableSnappingToSlotsOnAlt to be able to place items closer to each other. These were designed to be placed in a "Dive spot". You need Paradise Island to be able to place objects under water on the sea bed in a dive spot.
6 marine life objects
Swordfish-kissing gourami fish-lobster-polyp
Piranha-angel fish-jelly fish-blowfish-alley catfish
Joana's Deep - diving spot
Sea fan coral different types
6 shell fishes