In this story, there's a breed of Aquatic Marisa that escape to the deep sea. They live in depth of about 600-800 m below the surface and has adapted to the environment. When taken to the surface, these Marisa lost consciousness and bloats because of the internal paste pressure threaten to make them burst.
A researcher capture a family of deep sea Marisa to bait another creature, the Giant Iku. She appeared from the depth to torture and kill the Marisa slowly while bringing her victim to the "uneasy" depths. It's a parody of the giant squid feeding video by Japanese scientist.
In short, it's the "lolz, see that idiot yukkuri suffer and die! Not abyuse, this is science! lolz" category story.