The £13m  facility, which includes an eight-lane 25m (82ft) swimming pool,  opened on Aberavon seafront on Monday.
The Afan Lido was destroyed in a fire in 2009 and demolished in 2011.
Anthony Williams from Celtic Leisure, the company managing the centre,  said they had been "chocka since six this morning".
The new facility, which is next to the old Afan Lido site, has a 100-station gym, a large indoor sports hall, a smaller swimming pool  for learners and a cafe.
The original Afan Lido was opened by the Queen in 1965, and in its early days hosted major concerts by Pink Floyd and Spencer Davis, and in recent years Coldplay and McFly.
A new sports complex in Port Talbot has opened to the public more than six years after the town's lido was destroyed in a fire.