The Incredible Petrified WorldGoofs
The boat's crane extends over the starboard side. In reality, if a heavy diving bell is lowered over the side of a modestly sized boat, the overturning force will cause the boat to list severely or even roll over. For this reason, real boats used for lowering diving bells are generally equipped with a crane that lowers the bell through a hatch in the center of the boat's hull, or over the stern in-line with the hull centerline; this prevents the boat from rolling as the bell is lowered.
When Dale gets upset after reading a note from Tom, she throws her ring over the side of the boat. Even though they are far away from shore, the ring appears to land in water that's only around a foot or so deep. Not only does it look too shallow for a boat that size, but within minutes the diving bell is lowered into water deep enough for the bell to be down over 1700 feet.
Characters are seen climbing down the ladder into the diving bell interior before the dive, but the diving bell prop has no visible hatch on the top, nor any apparent provisions for the crew to climb aboard while it hangs from the ship's crane; in fact, the prop hangs from a hook that attaches where the top hatch should be.