Wow, we went to St Lucia, my wife’s cousin lives there. This was 20 years ago. The public beaches could be a little problematic due to semi aggressive peddlers trying to sell you tat.The snorkelling I do like, I am not a strong swimmer but can manage a snorkel.
We were very lucky to have turtles in the sea at the hotel beach, and saw a load of baby turtles hatch on/in the beach. Doubt whether that will happen this time , but I am looking forward to warm sea.