Flic en Flac is the big beach on the west coast: several kilometres of sand, a calm lagoon, and filao trees giving shade right down to the water.
This is where Mauritians come at the weekend, which gives it a very different feel from the touristy north. The diving is well regarded, and so are the sunsets.
I have one address here for now. If you are set on the west, tell me early: I can look beyond what is online.