A memorial stone in remembrance of Mr Marshall at the quarry
An MP has urged a diving website to remove "ghoulish" messages offering advice on how to explore a "dangerous" quarry containing the body of a diver who has never been found.
Elfyn Llwyd criticised the messages on UK Diving's website about the perilous Bryn Hall, near Bethesda, which contains dumped unexploded World War II bombs and barbed wire in its 50m murky depths.
It is the grave of a Merseyside diver, Andrew James Marshall, whose body has never been recovered despite considerable efforts, after an ill-fated dive with friends during the 1970s.
Mr Llwyd, Plaid Cymru MP for Meirionnydd Nant Conwy, said: "Bryn Hall is a very dangerous place and to see advice on what to do if you get snagged and that there is a body floating around there is all rather ghoulish.
"If the munitions aren't explosive and can't be detonated, then they are certainly poisonous and toxic.
"If these remarks weren't so flippant and the matter wasn't so serious, it would almost be funny."
The messages on www.ukdiving.co.uk have been posted by divers offering tips on how to explore the privately owned site as an alternative to another perilous Gwynedd quarry, the Dorothea in the Nantlle Valley.
Dorothea's icy waters have themselves claimed five lives in the past year and about 20 in the past 10 years.
The place is deep, dark full of barbed wire, unexploded bombs, not forgetting the poor soul still in there tangled in the wire.
Posting on the UK Diving website
A diver called 'sheepboy' writes on the website: "Be very, very careful in Bryn. You won't just need a knife to cut your way out, if you get tangled, you will need wire cutters.
"The place is deep, dark full of rubbish, barbed wire all over the place, dead sheep, cars and unexploded bombs and not forgetting the poor soul that is still in there tangled in the barbed wire.
"if you really want to dive it take a rope as it makes access a lot easier, vis (visibility) brilliant down to 30m, lots of quarry workings.
"Don't touch anything as it kicks up clouds of silt, down towards the 50m mark.
Mr Llwyd is calling for a diving centre to be developed in Dorothea
"The water turns into a black soup with zero vis. I don't know if this is something to do with the chemicals coming out of the bombs, flares and shells."
Another diver writes: "Bryn Hall is bitterly cold all year round and... the slate itself is razor sharp and will cut without warning so be extra careful.
Philip Osman, managing director of UK Diving Limited, said: "We are not encouraging people to dive in Bryn Hall, but if someone is intending to - and divers will dive in a puddle if they can - they need to know that there are considerable dangers there.
"If you read the postings they are actually a warning and not an encouragement."
Mr Llwyd is calling for the Dorothea quarry to be turned into a proper diving centre with a decompression chamber.