Just got back from St. Thomas (11/`21) and we had a great time.  I'm an avid snorkel fan with intermediate experience.  Secret Harbor Beach is rated as a MUST DO of the 5 beaches we visited (Sapphire, Coki, Magens Bay, Secret Lindquist being the other 4).  While I would definitely consider staying there some day, we stayed at Sapphire Beach this time.  The beach is smaller, not terribly crowded.  $20 to rent an umbrella and lounge chairs for the day (with towels).   Secret Harbor seems to be known as one of the most CALM beaches, even on bluster rough ocean days.  It's tucked away nicely and the water is beautifully clear, calm and shallow.  Great for kids.  We got there around 12:30 pm and immediately went the "The Patio at Sunset Grille" for lunch.  Unbeatable views (IMHO).  Slow service, but good food, right overlooking the beach.  Truly a must do.  We stayed all afternoon.  I snorkeled both the right and left sides.  Both were good.  Be sure to go out to the rocks on the right, really beautiful.  Several fish, 19 squid, spiny lobster to the left side past the point.  Lots of little brain coral to the left, like basketball sized mushrooms.  The beach is a gem.  We found parking 30 yards away from the restaurant no problem.  Watching the sunset from this beach is fantastic!  We stayed all afternoon and finally went back up to the restaurant for sunset drinks before leaving.  There is a dinner restaurant across from the The Patio that is much pricier and nicer.    Hope you make it there...it's a beauty!