A turtles shell scales grow larger as it ages. So the heart with the initials J+M that Magnus carves into one of the turtles scales should have stayed in that one scale. But when we see a close up of the giant turtle at the end, the heart and initials are now covering parts of four different scales.
At night following the first boat trip, after Magnus has dived too deep following Jennie, the 10-second overhead shot with her resuscitating him on the beach has video (waves) rolling in reverse. Maybe artistic intent on the moment, and/or re-edit to get the shot zooming in instead of out.
Eric (Carl Weathers) incorrectly pronounces Coelacanth as "cola-canth", not "seela-canth".