The group (SAS) says there were 95 “sewer overflow discharge notifications” affecting North Bay, and 46 in Runswick Bay, in the 12 months to September 30.
SAS say the country's waterways and coastline are plagued by combined sewers, which mix sewage effluent with surface water runoff into drains.
The discharges are designed for emergency use only, taking the pressure off treatment plants in exceptional circumstances and during unusually heavy rainfall.
Steve Crawford, long-standing SAS representative, who runs Fluid Concept Surf School in the town, says the problems happen all year round, despite Yorkshire Water (YW) investing £50m towards improvements in 2013.
Earlier this month he lost £400 when he had to cancel a class for a group of students “due to the water quality being so bad that it would be a risk to human health to take anyone in”.
He said it was now affecting more people because numbers of swimmers, surfers and paddleboarders had soared during the Covid-19 pandemic. Better information means they can decide whether or not to go into the water, but when he has found himself in the middle of a discharge, with “all the stuff that goes down the loo”, the worst thing was the smell.
Rather than a wonderful briny smell, “it smells like you are next to a sewer. It’s not something you really even want to think about.”
SAS says a total of 5,517 notifications were issued by water companies over the 12-months - an 87.6 per cent increase on last year’s figure of 2,941.
More than half were in the bathing season. Southern Water was by far the biggest culprit, issuing 1,949 notifications.
SAS chief executive Hugo Tagholm said successive governments promised action but firms had been aided by loopholes in laws and “systematically defunded” regulators.
He said firms “continue to increase profits whilst causing catastrophic damage to river and coastal ecosystems, with limited consequences.”
Earlier this month the Environment Agency (EA) and water regulator, Ofwat, launched an investigation after checks revealed that some firms may be releasing unpermitted sewage into rivers and watercourses.
Geraldine Tebb, coastal delivery and engagement manager at Yorkshire Water, said they had worked with other stakeholders on improvements at Scarborough North Bay and Runswick Bay over recent years. Both are rated as having excellent bathing water status by the EA.
She said: “We are committed to further improving the environmental performance of our wastewater assets and continue to innovate and invest in new technology and cutting-edge marine science to help maintain and improve bathing water quality in our region.
“Pollution on our coast is not something that we or our customers want and reducing intermittent discharges from CSOs is a key priority in our future plans.”
Earlier this year Scarborough's South Bay narrowly escaped being axed from a bathing waters list because of coronavirus, after being rated as 'poor' every year since 2016.