A report on the quality of UK beaches has revealed that the main beach in Weston-super-Mare received a pass.
The Marine Conservation Society said it would raise the standard in 2015 and predicted that some beaches might fail in future as a result.
The Uphill Slipway beach also received a pass while Sandbay beach received a gold award.
Wessex Water said it was currently investing £26m in order to help clean up the water in the area.
Dr Julian Dennis, director of appliances and sustainability at the firm, said: "We are making these investments so we do our bit to ensure that the bathing water meets a standard.
"Others must do their bit to protect bathing water quality - not just us."
Dr Dennis said Wessex Water was working with the Environment Agency on a project to improve water quality in the area.
He said overflowing sewage was thought to be contributing to the poor water quality.
He said the company was installing tanks to capture rain fall and the extra water that came into sewers to prevent overflows from going into the estuary.
He said the project should be finished by the end of 2012.
Rachel Wyatt, the pollution officer for the Marine Conservation Society, said: "There are a number of beaches that when we have these new stricter standards come in in 2015 that are actually predicted to fail.
"We're really asking environment agencies and water companies to work together to investigate what problems might be effecting these beaches which are likely to not meet the new standards."