If you drop the mooring and don't find another at Trellis Bay, plus don't wish to anchor then you have the option to head around Monkey Point on Guana and take a mooring at White Bay on Guana - those don't often fill up. Or if the rolling is due to a north swell then I'd head into the North Sound for a calmer anchorage or if you are at Guana Island already then continue to the shelter at Diamond Cay on Jost van Dyke.