The arsenal was discovered wrapped in a yellow reflective jacket and weighted with different stones.
Douglas, 29, used a powerful "two-sided magnet" that can lift 300 kg to lift the bag with a pump action shotgun, two pistols and ammunition.
Part-time hairdresser Sarah, 29, explained how it was her first time with Douglas, who discovered the hobby – in which magnets are used to retrieve metal objects from channels, rivers and lakes – from YouTube videos.
"He really became interested and the children followed him," she said.
"They all like it very much, they tend to go every weekend and do it for about two months.
"They get a lot of pedal bikes, shopping carts, watering cans that are on the back of boats.
Sarah said: "One of the guns was a completely black pump-action gun and there was still a casing in it.
"Another was a full metal and black pistol type, the last one was a different gun – it could have been a revolver, it took 10 minutes for Douglas to come out of the lake. & # 39;
The family, from Stoke-on-Trent, brought the find to the authorities.
Sarah said: "We handed the weapons directly to the police and left them with them, we did not hear anything else about them – we do not really want to know them."