Over two in three of the UK's beaches have got the top award for clean water in the Good Beach Guide.
The latest edition says UK beaches are getting cleaner.
But experts are warning that recent heavy rain might mean more sewage washing into the sea.
That's because sewer pipes overflow into rivers and the sea when rain pours into drains in the street - and poo and other things go straight into the water.
The Marine Conservation Society says 31 thousand pipes around the UK let sewage into the sea.