Large vessels cannot reach shore due to their low draught. So, a ship will normally drop anchor to keep from drifting on the tides and wave, then a small launch or a dinghy would take the crew to shore.
When sailing, if the ship should cross into the lighter blue water around an island's perimeter it is in danger of running aground and the Drop Anchor option will appear. Simply click on the Anchor icon to dock. You MUST drop anchor in order to unload plunder and receive your share of the cargo.
All crew will immediately arrive on the island's nearest beach or dock.