When Delmar wades into the lake with the grenade, between the close-ups of his face and the shots of him and the creature, the water height changes constantly.
When you see Delmar going into the lake with the grenade his shirt is already wet up to his chest, it shouldn't be. However when they switch between cameras his shirt is not wet.
When Delmar Coates is checking Lott Dryer on the deck for other weapons, he is supposed to have died from Cyanide yet you can see him breath, and his eyes flicker.