A Klingon Battle Cruiser with the cloaking device engaged transported them into a giant aquarium made of 12 inch thick plexiglass (because transparent aluminum hasn't been invented yet). And it wasn't a moment too soon, because a planet destroying probe is headed toward earth because it lost contact with the whales when we hunted them to extinction in the mid 21st century, and the radio waves it was sending to try to reestablish contact would have caused massive destruction to the planet.
They probably would have reached open sea sooner if Marine Biologists weren’t playing “Whale Sounds” at them that said, “don’t go that way, there’s nothing but Japanese Whaling Ships out there!”