In that case, Uswetakeiyawa beach is the best place. It’s like a swimming pool extending out for about 100 meters. Because there's a reef barrier further out, you won't get dragged away by the waves. It's not deep either around 4 feet maximum. Even little kids swim there. It's super chill around sunset.
There are a few swimming spots at Uswetakeiyawa beach, but in my opinion, this is the absolute best one. It’s literally like a swimming pool https://maps.app.goo.gl/aMh5d5aY5zi2EvWd7