Tenby Leisure Centre swimming pool is due to close temporarily later this month.
The closure is to enable a major £1.5 million upgrade of the centre.
Due to be finished in the Spring of next year, the refurbishment will include a brand new fitness suite and cafe, a Fit for Life library, a fully refurbished sports hall and dance studio, upgraded changing rooms and a new open-plan reception and foyer area.
However, the building work will result in some disruption to users in the run up to Christmas.
In particular, the swimming pool will have to be closed from 23rd November until 27th December.
Councillor Elwyn Morse, Cabinet member for sport and leisure apologised for any difficulties caused by the temporary closure.
"This will be an inconvenience to local pool users in the short-term, and we are sorry for this," he said.
"However, it is necessary to ensure the safety of our customers at this stage of the building works."
He added: "When the work is completed the Centre will be a huge asset to Tenby and a great resource for local users."
Tenby Leisure Centre manager, Darren Bowen, also apologised for any inconvenience.
"We will need to close the pool during this period to allow building work to be carried out as quickly as possible and without risk to our customers," he said.
He added that parents who had booked swimming lessons during the closure period had been contacted and advised of alternative arrangements.
Anyone affected by the disruption and wanting more information can phone 01834 843575 for more information.
The Tenby project is the final part of a ten-year £20 million investment programme into leisure facilities by Pembrokeshire County Council.
*The Learner pool at Tenby Leisure Centre is currently closed in a separate incident. It is expected to remain closed until the 27th December.