The ship will typically sail at nights, allowing passengers a full day of excursions at the ports of call.
Most sea cruise will start and terminate at the same port, but there are also cruises that only sail one way, for instance if you want to go on a cruise that transits the Panama Canal.
The cruise ships used for sea cruises are generally quite big, often they can carry more than 1,000 passengers at a time, but some are smaller and typically also more exclusive. In certain areas the cruise ships are small because of the cruise destination itself. I for instance you want to go on a Galapagos cruise most ships will only carry around 150-100 passengers, and some a lot less. The same apply for some cruises in Australia or the South Pacific Ocean.
Some of the cruise destinations are very seasonal due to weather conditions like temperatures, hurricane or typhoon seasons, and monsoons and so on, so make sure to check before planning.
Most passengers want to go in the high season and it is advisable to book well in advance if this is the time you also want to go. It can make a big difference for your experience what cabin you get, and the earlier you book the better the choice. If you want to book late, the risk is that all is already fully booked.
Today it is possible to go on a cruise holiday to destinations on all seven continents, which includes Antarctica. Some destinations are more popular than others; among these are the Caribbean, the Mediterranean, the Baltic Sea and Alaska.