Leeway: The "lee" is the area downwind of a vessel. A lee-shore is a shoreline that the wind blows on to, as opposed to a windward shore that the wind blows off. To give leeway is to allow enough room for a vessel to be blown off course by the wind and avoid danger.

Rig (noun): The mast and supporting stays on a boat. (oil rigs, "big rig" come from this I think).

Rig (verb): To put the sails up and tie on the sheets and other lines that control sails. ("Let's rig this up." == "Let's set this up.")

Posh (my favourite, though I doubt it's actually true): Port Out Starboard Home. When travelling from England to India around the tip of Africa, it was favourable to have a cabin on the port side on the way to India and starboard on the way back as it would be in the shade most of the time and a little cooler in the sun, with a view of the land.

See also: Change tack / try a different tack, right the ship, stay the course, (to be) swamped, "At a rate of knots" (very fast), keep an even keel, keel over.