We stayed at the St Regis resort and had dinners in each of their restaurants, but Lagoon is by far the best (which wasn't a surprise!). The service was exceptional and the food was very upscale and delicious. A newly married couple was eating near us and had a musician playing a ukelele which made for great, subtle entertainment. You'll definitely want to ask for a table on the deck. Ours was on the higher tier which made for great views but also let us look through the glass floor to see the sharks and fish swimming underneath.
This is one of those restaurant experiences where you just indulge and sign the check blindly!