Goofs

Marsha's hair and lipstick are perfectly dry immediately after she surfaces from her deep dive.

When the creature jumps into the boat, he is shot in the left side of his chest with a spear - then a moment later the spear is on the right side.

When the Creature grabs Dr. Barton to throw him off the balcony, potted plants are seen on the balcony railing. In the subsequent wide angle shot, the plants are missing.

Dr Borg identifies a trace on his sonar as a school of Rock Lobsters. Lobsters do not swim in schools.

At one point Dr Borg states that he can tell the exact species of fish from its sonar reflection. This is impossible with the technology shown, as the display only shows a blob of light, without any fine detail.

Dr Borg's sonar shouldn't be able to work in shallow water due to confusion from reflections from the river bottom and sides. Nevertheless, it is shown to be able to detect the Creature moving in fine detail.

Biologist was looking at a sonar screen NOT the wall chart when he describes the Creature as appearing "half a centimeter taller than the average adult male". Also, half a centimeter, less than 2/10 of an inch, doesn't match the wall chart. More likely the line should have been half a meter taller.

When the creature throws Dr. Barton from the balcony, the wire holding him flashes in the light.

When the creature lifts Dr. Barton on the balcony to throw him to his death, two wires can be seen to allow for the actor playing Dr. Barton to be so easily lifted.

At the climax, when the creature escapes and begins throwing furniture around, you can see the wires attached to the pieces of furniture.