The Skipper
While onboard the skipper is in overall charge of the safe operation of the vessell. He is head of the vessel and the mate directly reports to him. His duties and responsibilities include:

The Mate
The Mate is second in charge of the vessell, if for any reason the skipper is unable to take charge of the boat the duty then falls to the mate.
Standard duties and responsibilities of the mate include:

The Watch Officers

The Watch Leaders