The Mystery Sub was a mysterious craft that Stingray defeated that appeared to have no crew.
The crew of Stingray first encountered the sub a short time before Christmas. They fired a torpedo at it and crippled it, causing it to sink to the bottom. When they boarded the sub, it was mysteriously empty, with no visible crew or anyone on board. It was then towed back to Marineville for further investigation.
While the investigation continued, the decision was made to recreate the battle between Stingray and the mysterious sub. With Troy piloting Stingray and Phones in the mysterious craft, they set out to recreate the battle.
Unbeknownst to any of the Marineville staff, a subterranean has been hiding behind a door disguised as a control panel the entire time. He sneaks up behind Phones, knocks him out, and then ties him up. After seeing the torpedo tube opening on the front of the mysterious sub, Troy has Barry Byrne, who is riding along in Stingray with him, launch him out of the torpedo tube towards the sub. Troy then enters the sub and wings the enemy with his gun, stunning him.
- This model is made from a plastic ship hull with various parts from other kits and balsa wood added.