We live along the Gulf Coast. We know what a beach looks like. It has sand and pretty water. Of course, everyone warns you but it's true: This beach has no sand, just a lot of broken shells, and it's extremely small. If not for its proximity to Do's or Gustavia, there would be no reason to go here.
We stopped at St Barts on P&O's Adonia, The beach is shells and no sand, We preferred to walk around the town and look in all the shops, people warned us about the cost of sunbeds, so we admired the water and the boats from a bench on the quayside, it was very hot the day we arrived there but...
The beach is pretty, the water clear. There is a restaurant and the people are awful, rude, unpleasant and generally horrible. Avoid them. Definitely don't get conned into paying 40 euros to sit in their chairs!