Curtis's death. One of the Snappers cracks her helmet. Just as she and the group reach the underwater base it begins to break. Jiuming grabs her and tells her it will be okay, only for her helmet to implode due to the water pressure, violently crushing her head while everyone, including Meiying, can only watch in horror. Mind you, this happens seconds before the decompression process that would have saved her finishes itself.
The Meg rampage on Fun Island includes shots from inside the Meg's mouth. Terrified screaming swimmers are swallowed whole, meaning at best they will drown and at worst will survive just long enough to start being digested. The ones that Haiqi ate will likely be digested; the ones eaten by the Megs that Jonas killed probably drowned or, in the case of the one he took out with the explosive harpoon, got blown to kingdom come if they hadn't been swallowed all the way down yet.
While it was a given that the Megs would escape to the surface, for those who weren’t spoiled beforehand in the previews, something else also is shown rising through the thermocline, obscured by the darkness, and what appears to be smoke. Upon closer inspection, it turns out it’s not smoke, but ink.
