What do I need my crew for?
Each crewman gives a bonus that depends on his profession and level. You can collect experience for them every time you use their abilities.
What is the Doctor's function and how can I advance him to higher level?
Doctor increases the amount of Health Points that you get while exchanging Energy into Health.
When the number of your Health Points drops below 30% of maximum, the ADD button shows up under the Health bar. After using this option you will get experience for Doctor. Further levels of his experience allow you to gain more Health Points for the same amount of Energy Points.
What is the Energizer's function and how can I advance her to higher level?
Energizer increases your maximum available amount of Energy Points by 1. Experience fo Energizer will show up every time you spend some Energy, eg on harvesting cargo or opening barrels.
What is the Gunner's function and how can I advance him to higher level?
Gunner increases possible amount of damage inflicted with single shot. Each time you sunk a ship (NPC's or a player's), you get experience for Gunner.
What is the Fisherman's function and how can I advance him to higher level?
The higher level Fisherman has, the more he increases the amount of cargo gathered at once in fisheries. Each level gives +1 to this amount (on the 1st level you get 2 eels, on the 2nd - 3 etc.). Fisherman gets experience every time you use the fishery.
What is the Farmer's function and how can I advance him to higher level?
The higher level Farmer has, the more he increases the amount of cargo gathered at once in farms. Each level gives +1 to this amount (on the 1st level you get 2 mangoes, on the 2nd - 3 etc.). Farmer gets experience every time you use the farm.
What is the Huntress' function and how can I advance her to higher level?
The higher level Huntress has, the more she increases the amount of cargo gathered at once in hunting lodges. Each level gives +1 to this amount (on the 1st level you get 2 parrots, on the 2nd - 3 etc.). Huntress gets experience every time you use the lodge.
What is the Pearl Diver's function and how can I advance him to higher level?
The higher level Pearl Diver has, the more he increases the amount of cargo gathered at once in reefs. Each level gives +1 to this amount (on the 1st level you get 2 starfish, on the 2nd - 3 etc.). Pearl Diver gets experience every time you use the reef.
What is the Diver's function and how can I advance him to higher level?
The higher level Diver has, the more he increases the amount of cargo gathered at once in wrecks. Each level gives +1 to this amount (on the 1st level you get 2 pieces of porcelain, on the 2nd - 3 etc.). Diver gets experience every time you use the wreck.
What is the Miner's function and how can I advance him to higher level?
The higher level Miner has, the more he increases the amount of cargo gathered at once in mines. Each level gives +1 to this amount (on the 1st level you get 2 sapphires, on the 2nd - 3 etc.). Miner gets experience every time you use the mine.
What is the Trader's function and how can I advance him to higher level?
Trader increases the amount of money that you get for selling cargo. Each time you sell some cargo, you will get experience for Trader.
Why can't I advance my crewman to the next level?
Apart from experience, each crewman advance needs a certain captain level. If your level is too low, you cannot advance your crewman. You cannot also advance the crewman above 10th level.
Source: http://en.forum.tanadu.com/viewtopic.php?p=1922#p1922/Mia.