Video captures the scene as Captain Matt Wirt and his friend John Christopher dive down to the SS Papoose off the US state of North Carolina.
The ship was sunk by a German torpedo in 1942 with the loss of two sailors and has since become a haunt for sand tiger sharks, a normally docile species.
But the sharks were far from docile when Captain Wirt visited, stealing his fish and his spear, and leaving him defenceless against the predators.
The 42-year-old said: “Diving with sand tiger sharks is usually uneventful. They are large, powerful and intimidating, but are usually docile.
“It usually doesn’t play out like this. While they might show interest, they are usually just curious and then go on about their day.
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“But we could sense the tension after a while by the way one of the sharks was acting – it was becoming aggressive.”
In the footage, a shark stalks the two divers as they hunt for grouper, drawing closer and closer until they retreat towards the wreck.
Then, as Captain Wirt shoots another fish, a fully-grown pregnant sand tiger shark snatches his kill – and his spear – leaving him defenceless.
Soon another shark comes for them, charging twice as Mr Christopher, 33, defends them both with the remaining speargun.
“The same shark came at us both times,” said Matt. “It was looking to bite, and wasn’t going for our fins.
“I had the harvested fish on me still, so I positioned my self above my friend who still had his spear.
“I think the shark could smell the fish I had and came up for a meal. It usually does not play out like this but anything is a possibility underwater.
“In those tense moments I was surprised that this sand tiger was acting so aggressively as they are usually a non-issue. That was probably the biggest surprise.
“You only have a few seconds to make decisions. Looking back we both felt pretty lucky we got away from this shark and are able to laugh about it, watch the footage and learn from it.”
Captain Wirt, who owns Killing Time Spearfishing and Reel Adventure Charters, says he’s changing his equipment for future dives so he can quickly ditch his catch if a shark takes interest.