There are expedition companies that offer ship based tours all over the world. They tend to be expensive, but offer great value experiences. They are normally staffed by 6 - 15 variously experienced and interesting expedition staff. If you are of reasonable fitness, it is best to focus on those areas that are otherwise hard to access by land, and these offer the best value for money; e.g.: remote coasts such as the Kimberley, remote islands such as Polynesia and the subantarctic, and 'difficult' places such as Papua New Guinea...
As an expedition leader, biologist, lecturer and boat driver I am fortunate enough to be able to go out with some of the best companies in the world to some of the best spots in the world. Unfortunately, the companies come and go a fair bit, and most of the ships I have worked on have been renamed or taken over, as it hard to make money in this industry. For the last fifteen years and for the next few seasons, these are some of the companies I have/am working for...
I have worked with/on:
Silver Explorer (was World Discoverer 2)
Noble Caledonia & APT
Celebrity X Cruises (cruise ship)
National Geographic Orion (formerly Orion)
Orion 1 (now National Geographic Orion)
Spirit of Oceania
World Discoverer 2 (now Silver Explorer)
Coral Princess 1
Coral Princess 2
Captain Cook cruises
Frankland Islands cruise
Frankland Islander 2
(escorting tour guide on Quicksilver & Michaelmas Cay)