On a dangerous search for an underwater uranium deposit GI Joe is menaced by a whirlpool and killer sharks!  What is that glinting on the sea floor?

In The Shark's Surprise (7940) GI Joe was given a much simplified and non-motorized version of the sea sled molded in solid blue.  Most of the accessories in the set were also available in Danger of the Depths, and the treasure and chest were shared with Eight Ropes of Danger.

This set was available with or without a GI Joe figure.  Boxes that didn't include the figure just blacked over the 'figure included' text.  I have added a GI Joe to the box.  The 1969 red top box can also be found with a 1970 Adventure Team version of the set inside, apparently an attempt to use up surplus boxes.

Above and left, the 'figure included box language.  

​One of the best 1969 variations is the two-tone treasure chest, molded in brown swirl plastic with a separate silver plastic overlay to represent iron bands on the chest.  This could not have been available for very long, as the bulk of chests found are molded in the same solid brass colored plastic that was used for the Deep Sea Diver helmet.  This chest is found both in this set and Eight Ropes of Danger

Another variation is the first version of the white scuba tanks with a back plate like the earlier ones found in the Navy Frogman and Sea Sled sets.  Hasbro switched to a simple vinyl or soft plastic strap later, probably to simplify production.