Why does the anomaly in the lake only become visible – and stay visible – after the diver has swum through it?

Great lines:
Claudia: “It looks like a plumber was attacked in some woman’s cellar.”
Lester: “I’m not surprised – have you seen how much these people charge?”

Stephen and Abby are unpacking equipment outside the house. Why in the world would they need a sledgehammer?! Is it to cosh the mosasaur if it turns up in the cellar?!

Claudia comes into the house with the Special Forces divers. She has her coat over her arm. We switch to a shot of Stephen asking, “What’s going on?” and cut back to Claudia, who is suddenly wearing her coat.

Lester’s hairstyle changes dramatically between the beginning and end of the episode. Presumably the scenes at the house were filmed much later in the filming schedule.

They said the anomoly magnetic field was at 5 tesla.
Too much tesla can mess up a person's brain. I recall a guy on another forum telling a story about being part of a lab & they had a machine that could produce 5 tesla which they tested on a rat (it was scheduled to be food for another lab animal) & really messed it up with the magnetic fields.

Oh wasn't it amazing that the mosasaur somehow knew that that thing dropping into the water would be edible & managed to maneuver itself into a leap to catch him in mid-air. Especially since the chlorine should have been hurting its eyes & focusing on something climbing a ladder out of the water would have been difficult.

Also interesting because it later swam around Abby & Conner in the lake instead of quickly gobbling them up.

Well, it vomited up most of the swimmer, so maybe it had decided that humans - especially those soaked in chlorine - aren't very tasty! It avoided the divers too, but they were wrapped in rubber so would have been a bit chewy. ;-)

Which just made me realise: the anomaly opens 3 times in this episode, twice in water. What are the chances of an anomaly in water opening into another water environment? There's apparently no rule about this because the final one opens in someone's basement and so, if anything, it's a bit miraculous that the first two do find water to open into.