Captains are required to create convoys and automatic trade routes. They also watch out for storms and icebergs that could damage the ship they are on.
Usually there are at least two captains at any time available in random taverns (river towns are a good bet early on). If you hire one of them, a new one will appear in a day or so. If you don't hire captains for a long time, a lot of them will be available in the various taverns.
Captains have three skills: Trade, Sailing and Fighting; the level of each skill is rated from 0 to 5. Highly skilled captains are paid more gold every day. A Captain's age will help determine how long they will serve you, as they retire after a few decades.
Allows the captain to purchase goods at a lower price (there is no bonus for selling goods):
Trade 1 - 5% discount
Trade 2-3 - 7% discount
Trade 4 - 9% discount
Trade 5 - 10% discount
Works with: automatic trading. Doesn't work with: manual trading, Expeditions (expedition prices are randomly determined based on the time of sailing off the map).
Improves a ship's manoeuvrability and speed during combat.
Works with: combat speed and manoeuvrability. Doesn't work with: sea travel speed, expedition travel speed.