Second mate

A second mate (2nd Mate) or second officer (2O) is a licensed member of the deck department of a merchant ship holding a Second Mates Certificate of Competency, which is issued by the administration. The second mate is the third in command (or on some ocean liners fourth) and a watchkeeping officer, customarily the ship's navigator. Other duties vary, but the second mate is often the medical officer and in charge of maintaining distress signaling equipment. On oil tankers, the second mate usually assists the chief mate with the Cargo operations.

The Navigator's role focuses on creating the ship's passage plans. A passage plan is a comprehensive, step by step description of how the voyage is to proceed from berth to berth or one port to another. The plan includes undocking, departure, the en route portion of a voyage, approach, and mooring at the destination.

The GMDSS (Global Maritime Distress and Safety System) officer role consists of performing tests and maintenance, and ensuring the proper log-keeping on the ship's Global Maritime Distress Safety System equipment. Safety equipment includes Emergency Position-Indicating Radio Beacons, a NAVTEX unit, INMARSAT consoles, various radios, Search and Rescue Transponders, and Digital Selective Calling systems.