We just came back from an eastern cruise. Stops at San Juan, St. thomas and St. Maarten.
In St. Thomas we took a taxi, they are lined up as you get off the boat. For a total of $20 for 3 of us he took us for a 15-20 minute drive to Magen's Bay.
It is one of the 10 most beautiful beaches in the world, and it truly was! The water was so beautiful and clear...my daughter said it was like a swimming pool, and even tasted the water to see if it was salty!!
We rented beach chairs and 1 float, $25. We stayed about 4 hours and took a taxi back...they are lined up and waiting, so that was easy.
The bottom line is that we spent about $65-$75 for this adventure and saved a LOT of money from booking an excursion.
We talked to several people who took an excursion to Turtle bay and they were dissapointed...it was a long time to get there and they only had about 1.5 hours of time on the beach.
Have agreat time on your trip!!!