The net, spread over about 50m, is anchored to the bottom in about 17m at mean high water, rising 2m off the seabed. It remains there despite the fact that local regulations ban the use of nets in the Sound.
The net lies too deep to threaten yachts or other pleasure craft. Nor is it a threat to shipping, being situated near the Sound's Asia buoy, inshore of the channel leading into the River Tamar and Devonport Dockyard.
It remains a threat to divers, however, being positioned in an area frequented mainly by local people who enter from the shore for moderate-depth dives.
The diver who did just that and nearly drowned wishes to remain anonymous, but Dougie Allen, who runs Plymouth's Aquanauts, has confirmed that he is an experienced diver.
After swimming into the net toward the end of his dive, the individual struggled for 20 minutes - fortunately having enough air to do so - before managing to free himself, having expected to die.
Allen has told Divernet that, following the incident, the situation was reported to Plymouth's Queen's Harbourmaster by, among others, Aquanauts, with a request that the net be removed.
On learning from other divers that the net remained in place more than three months later, Allen and a colleague dived last weekend, 18/19 April, to inspect it for themselves.
The net, held down by weights and buoyed along its upper edge to keep it raised, had clearly been laid deliberately rather than accidentally lost - making it a mystery as to why its owner had not retrieved it.
"A load of dead fish and crabs were caught in it," Allen told Divernet. "A seal carcass, which the diver who got trapped had seen, was still there too, rotting away."
Allen has repeated the request for its removal and a newspaper reporter, who accompanied the net-inspecting divers, is publicising the issue locally.