Twill enters a car with a driver when leaving for the mortuary. When he gets there, he is driving the car and is on his own.
In the underwater "pool" where the creatures are supposed to reside, they are shown as Monoplacophorans, meaning they have a shell like a snail. When the creature is shown out of the water in both the office attack and lock attack scenes, it appears as a Polyplacophoran, meaning flexible plates on the dorsal side instead the carry-along shell.
After boat 242 is found deserted, LCDR Twillinger and LT Clemmons board her and find Sanders. When they boarded 242, there was no mollusk secretion on its plank, but as LCDR Twillinger comes back to plank to look in the sea, he places his hand in a white secretion. Obviously, if it had been there, they would have seen it (or slipped on it) while boarding.
As the recovery boat approaches the downed parachutist's location, the position of one crewman alternates between standing down in the cockpit with his arm wrapped around the radio mast in the center of the boat in closeup to standing above the cockpit on the starboard side of the boat in long shots.
When little Sandy is first speaking to the caged rabbit, it's quietly lying down; when the camera cuts away and a second later comes back, the rabbit is busily munching away.
While the creatures are supposed to be (and have the shells of) giant snails, their bodies have the segmentation, legs, eyes, and mouth-parts of insect larvae.
At around 9 mins A radioman is at his equipment wearing a sailor's hat. A hat would not be worn at a work station inside a building.
Despite the divers going deeper and deeper (from 65 to 125+ feet), the amount of light underwater never diminishes; in fact, it actually gets brighter.
Just prior to being attacked, the lock keeper's shirt is wet from a previous take.
After Jody is pulled under the water, the sound of his screams continues for about a second.
Action switches back and forth between the Salton Sea and NAS El Centro. These sites are about an hour's drive apart, but are represented as being co-located.
After the first boat fails to respond to radio calls, a second boat is sent out. The rescue boat finds the first boat which is boarded by the two officers. Momentarily there is a shot where land can be seen that appears to be just a stone's throw away. Subsequent shots have the camera angled so that mistake doesn't happen again.
The shoreline scenes show breaking surf. The Salton Sea is a lake where the waves never get more than a few inches high, even in a high wind.
At around 3 mins The pick-up boat spots the jump plane and radios the plane saying they have it in sight. The pilot responds, "Hollister now preparing to jump. Over and out." This is incorrect as the two terms are mutually exclusive. "Over" is used when a response is expected; "out" means the communication has ended.