It involves topics and development of specialised skills including: navigation and international maritime law; weather, meteorology and forecasting; watchstanding; ship-handling and small boat handling; operation of deck equipment, anchors and cables; ropework and line handling; communications; sailing; engines; execution of evolutions such as towing; cargo handling equipment, dangerous cargoes and cargo storage; dealing with emergencies; survival at sea and search and rescue; and fire fighting.
The degree of knowledge needed within these areas is dependent upon the nature of the work and the type of vessel employed by a mariner.
Source: https://en.wikipedia.org/wiki/Seamanship