I only anchored there once and brought up a lot of sticky mud with the anchor. Here's tonights forecast for Vineyard Haven (about a mile from Tashmoo)

Tonight(nl)Showers. Locally heavy rainfall possible this evening. Strong winds with lows in the lower 70s. Northeast winds 35 to 45 mph...becoming northwest after midnight. Gusts up to 75 mph. Chance of rain near 100 percent.