Weston's Marine Lake has been temporarily closed and drained due to safety concerns after a swimmer needed to be rescued earlier this week.
On Wednesday 21 July, a bather became stuck in the mud at the site and had to be rescued by North Somerset Council's seafront rangers.
Now, North Somerset Council has decided to close the lake and drain it - because the water quality has deteriorated.
'Confident this won't happen again'
Cllr Mike Solomon, North Somerset Council’s Executive Member for Neighbourhood and Community Services, said: “With the current spell of hot weather, we're seeing increased usage of the lake.
"Although we've been able to remove a lot of the built-up silt within the lake during the spring, the majority still needs to be removed when we've got the permission to do so.
"While we'd hoped to be able to re-open the lake for the whole summer, yesterday's incident and the water quality means that we have to rethink.
"I'm pleased to hear that the person who became stuck yesterday is OK. We need to be confident that this won't happen again. Public safety is paramount.
The council is working closely with Weston Marine Lake Mudlarks on the future arrangements for the lake.
Claire Trevor-Roper, one of the directors of the Mudlarks, said: "It's such a shame that we need to close the lake again right at the start of the school summer holidays, but given the volume of silt that still needs to be removed from the lake we shouldn't be surprised.
"This is a temporary issue and we'll continue our work with the council to ensure that the lake can be restored and enjoyed by many people for years to come."
Marine Lake recently reopened for the summer season following the first stage of a £300,000 project to improve the popular community facility.
High tides are normally used to 'flush out' much of the lake's silt.
An application to mechanically remove 30,000 tonnes of silt accumulated silt has been submitted to the government's Marine Management Organisation with an outcome expected in the next few months.
Clevedon's marine lake is also temporarily closed and drained due to deteriorated water quality with refill expected on the weekend's high tides.