The zodiac rides can be as little a a few minutes to get from the boat to shore, or they could be full zodiac cruises of an hour or more.

When you go to the Trip Advisor Antarctic Adventures FAQ site referenced above by PerfectlyPerth, be sure to check out the Trip Research site which compares various operators, seasons, destinations and so on. There are many more choices for trips with landings than National Geographic.
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Sailed:
Eden (Navimag) four nights on ferry up inner west coast of Chile, March 2016
Expedition (GAdventures) Antarctica, Feb/March 2016
Dragon's Pearl Halong Bay, Vietnam 2014
Azamara Quest Far East, March 5, 2011
Victoria Empress, Yangtze River, March 25, 2011
Azamara Quest Ancient Empires, Nov. 14, 2009

Independent land tours:
Skiing in France, then drove to Tuscany, down to Sicily and back to Lyon: six weeks, March/April, 2017
Argentina and Chile - cities and Patagonia, 2016
Cambodia, Myanmar, Vietnam and Seoul, 2014
New Zealand and Australia 2013
China 2011
Argentina and Peru, 2007
Europe, 1985, 91-92, 95, 2001, 2003, 2008, 2011
numerous in US and Canada
Guatemala and Mexico 1971, 1972
Haiti, 1970
Jamaica, 1968-71

Next:
Safari in Tanzania; Victoria Falls; train to Pretoria; train to Cape Town - with stays in Amsterdam going and coming. fall, 2018