The depth of the sea lab changes. After the earthquake Capt. Williams reports to Halifax the lab was at less than 250 feet. During the briefing with Commander Blake Dr. Andrews says the seamount was at 120 meters, which is just over 390 feet.
This depth is confirmed when Blake reports he is holding the Neptune above the lab site at 100 meters.
David Yorston's character's name is spelled Stevens on his scuba gear, but it's spelled Stephens in the end credits.
The helicopter Cmdr. Adrian Blake rides from the airport in Canada is different from the one that delivers him to the ship. The helicopter at the airport is powder blue, while the helicopter that delivers him to the ship is dark blue.
Neptune's crew was able to watch through the submarine's glass window all the objects and fish around them under sunlight although they were deeper than 300 meters from the sea surface. Sunlight is barely seen in the sea bottom at depths greater than 200m.
The Air Canada DC-8 presumably lands at Halifax, N.S., and then Cmdr. Adrian Blake is airlifted to the Trident. The coordinates given earlier in the disaster would make this distance 700 miles. There is no way that helicopter could fly to and from the ship at that distance.
When Dr. Leah Jansen is suffering the effects from going too deep, she is heard talking through the ship's speakers. However, when Cousins and MacKay rescue her, her scuba gear is shown to have a standard mouthpiece and her face mask only covers her eyes and nose; this would have prevented her from talking to the ship.
(at around 57 mins) When Cmdr. Adrian Blake enters the sub for the second time, he is wearing a tan shirt; once he is in the sub, he has on a blue shirt with a red sweater.
A black-suited diver is briefly shown assisting 2 others to depart from the lab in a mini-sub. He's not one of the characters, and he disappears from the scene when the next diver (Yvette Mimieux) exits the lab to follow the sub.