I only remember one scene from this movie: a man on a boat (small yacht?) is seemingly floating in air when he is first found in a cabin by another character. The other character freaks out because of the floating guy. Later it is discovered he has actually been impaled by the bill of a marlin in an adjoining cabin, which was thrown about by the rocking boat (perhaps during a heavy storm). The marlin's bill went through the wall and killed the man in mid-air. From the angle of the door to the cabin, it looks like he is floating.
This movie was probably made in the 70s or maybe early 80s, and it may have taken place in the Bermuda Triangle. If I remember correctly, it had a creepy horror feel to it. It was in color.