Find a library, or get a copy of "Chapman's" [Chapman Piloting & Seamanship] and you'll get a lot of useful information fast, especially the names of things on and off the
boat, and proper procedures. One of the many
books on knots will also let you surprise him.
Navigation and systems gets a bit more complex, and sailing itself is best learned "hands on" rather than through the confusion of new words in
books. "Colregs", the
Collision Regulations, which also include right of way rules, lights and shapes, is available directly online and if you learn that stuff--guaranteed he'll be surprised and pleased. If he races, there are
racing rules also available online, and again, he'd be floored if you knew them.