Visible crew/equipment: After Calvin Bouchard makes the announcement to tourists visiting the Undersea Kingdom to evacuate, we see the tour guide lead the crowd through the tunnels. The green screen backdrop is still in the final cut. They forgot to add in the underwater effect.
Visible crew/equipment: When Mike fires the harpoon at the shark, the wire the arrow is attached to is visible. (00:45:05)
Visible crew/equipment: In the opening credits we see shots of water skiers climbing on top of each other to try and form a human pyramid. In one long shot you can see the side of the wake which the crew's speedboat is making. (00:02:35)
Answer: The lagoon was part of the theme park. Artificial with specific mammals inhabitants inside, warm and friendly.