No one was injured in the incident, but the 33 metre main pool at the Aquarena sports centre in Worthing has been closed until full safety checks can be undertaken.
The facility is operated by Worthing Borough Council and a spokeswoman said: “We are going to make sure all grilles are completely safe before reopening the pool.
“We are waiting for the contractors to make time to come and undertake the work.”
The council is expecting the pool – which receives 500,000 visits a year – to be closed until at least next week. All other Aquarena facilities will remain open.
The council has come underfire for the state of facilites with Lib Dem borough councillor Bob Smytherman describing the incident as “outrageous”.
However, the council spokeswoman said the council had a long term aim to replace the pool.