A sailor, although most of the evidence relates to men who operated boats on the Ouse, the Trent and their tributaries. Several villages and towns in that region were ports.
Land by a river (OED), or a precipitous slope (PNWR7/242). Research by David Shore suggests that it was more accurately ‘an arc of rising land above a river or stream’.
In contexts which relate to water mills, reservoirs or drainage systems, a ‘shuttle’ was a flood-gate; that is a hatch or ‘door’ which controlled the flow of water and needed to be raised to allow it to flow freely.