Hello Shellyjo, welcome to the message board.
There aren't any water parks in the U.S. Virgin Islands of the variety you are asking about... with lazy river. There is a very small kids waterpark on St. Thomas with special hours and/or reservations necessary to have it open. Of course all the islands are surrounded by water so lots of water sports and water based fun to be had: power boating, SUP, kayaking, sailing, diving, snorkeling, kite boarding, wind surfing and so on.
Most of the resorts having swimming pools, some have features like small waterfalls but no lazy rivers.
Thank you for using VInow.com to help plan your USVI vacation.