They're the best I've come across but your best bet would be to give the ferry operator a call and check before making plans. What difficulty did you encounter?

We read in St Thomas Weekly that they went out during the week.
We arrived in Red Hook on a Tuesday morning only to find they did not.
However, because our party was so large they arranged a boat for us which was a great show of hospitality.
Family members that had never been to St Thomas loved it.

I don't think the Water Island ferry schedule is 100% accurate. Seems like I checked it before I went to Crown Bay on Tue or Wed, and I thought the schedule said it was leaving at 5. It left at 5:15. I may have missed a connection waiting for the ferry to leave at 5.

All schedules are subject to change, so STT's advice is the best - call ahead to make sure. Anything can happen.