Pinnace
A pinnace is a light boat propelled by sails or oars, formerly used as a tender for merchant and war vessels. In modern parlance pinnace has come to mean a boat associated with some kind of larger vessel that doesn't fit under the launch or lifeboat definitions. In general the pinnace had sails and would be used to ferry messages between ships of the line, visit harbors ahead of the fleet with messages of state, pick up mail etc.