An environmentalist who dedicated himself to cleaning beaches is hanging up his litter picker because of a "losing battle".
Alan Cookson, 46, from Aberystwyth, estimates he has cleaned more than 120 beaches as a volunteer with Surfers Against Sewage (SAS).
Mr Cookson said it "breaks his heart" to stop but fears it is too late to save the oceans from plastic pollution.
He also accused pressure groups of competing, rather than collaborating.
By his own admission, Mr Cookson "doesn't stop" picking up plastic when he is out and about, and estimates he has cleared - individually and as part of groups - at least 5,000kg (five tonnes) of plastic from Welsh beaches.
But after four years as a regional SAS representative for north Ceredigion, he has given a bleak assessment as he steps down to spend more time with his family.
"The reasons are many: we're losing, or we've lost," he said.
"When I started it was estimated that 8,000 tonnes of plastic entered the oceans every year and there was 5.5 trillion pieces of plastic polluting them.
"Now, as I stop, the numbers are 10,000 tonnes a year and 50 trillion pieces already in there and unrecoverable."
He slammed governments and big business for failing to take the problem seriously, adding the world's oceans are "dead, or soon will be".
But Mr Cookson also criticised the environmental voluntary sector.
"In my four years I've seen Surfers Against Sewage, The Marine Conservation Society and Keep Wales Tidy compete for the same pools of money, replicate each other's campaigns and generally carve each other up rather than support each other.
"Each individual organisation is trying so hard to justify its own existence that they don't want to cross co-ordinate because it weakens its own existence."
Surfers Against Sewage said it does not recognise Mr Cookson's assessment but welcomed his contribution to the "wider conversation".
"We collaborate with many, many charities," chief executive Hugo Tagolm said. "But no one in the charity sector thinks one homogenous charity is the way forward."
The Marine Conservation Society said it "prides itself on collaboration with other organisations and campaign groups".
Keep Wales Tidy said partnership is "essential to everything we do".
Mr Cookson added: "It breaks my heart to stop, but I have three children who have missed too many [weekends] with their dad because he was fighting something he thought we could beat."