The divers were exploring the C-53 wreck off the coast of Cozumel in Mexico when they heard an approaching noise.
Troy Knabe was one of the divers who managed to get his camera out in time to capture footage of the submarine.
The video of the mysterious encounter was posted on Reddit last week and has already been viewed by thousands.
The submarine appears to be around 30ft in length, with a wood decking, white paint, a standing platform and handrails across the top deck.
The mysterious video caused quite a debate amongst viewers, who have been trying to identify the sub.
According to many, the features of the vessel point to the fact that it is civilian.
It was later identified as a tourist submarine belonging to the Waikiki Atlantis Submarine company. The vessel takes visitors to Hawaii’s Oahu Island on a journey through the ocean.
Some viewers said that they would have been terrified if they were the divers who witnessed the sub pass by so close to them.
“That would scare the hell out of me! I mean, diving, in general, seems terrifying, but this would be otherworldly.”