But in fact there are just seven iconic 'must do' cruise journeys - and here they are.
1. Transiting the Panama Canal
I've been through plenty of canals in my time, from the engineering wonder that is the Gota Canal in Sweden, to the magical 'touch the sides' journey through the Corinth Canal at dawn. Great experiences, but they don't even come close to the excitement of entering your first huge lock as you leave the Pacific, with glorious lush scenery on either bank, or the close-up inspection of the other vessels as you cross the Gatun Lake.
2. A Transatlantic crossing to New York
When you can fly from London to New York in just a few hours, why would you go by ship? There is something romantic in recreating the glamour of the transatlantic crossing, a nostalgia hearkening back to the days when ocean travel was the only option to travel the world. The imposed relaxation of six consecutive days at sea gives you pause; time to reset your body clock. Best of all, at the end of your trip, sailing up the Hudson River, under the Verrazano Bridge and past the Statue of Liberty, makes a phenomenal finale.
3. Crossing the Drake Passage to Antarctica
The Drake Passage has a fearsome reputation as one of the world's roughest waterways, with surging currents, buffeting winds and powerful sea swells where the Atlantic, Pacific, and Southern Oceans meet. It is your rite of passage, though, to reach the magical calm and breathtaking beauty of Antarctica, like travelling to another world.
4. Cruising the Norwegian Fjords
A sepia postcard from my great grandmother's box of treasures shows the glassy, still waters of Geirangerfjord, with the majesty of the sheer cliffs and a picturesque village nestled at the water's edge. This timeless landscape, unchanged over the years, has lost nothing of its captivating power. A land that can be reached only by sea evokes the ancient journeys of Viking heroes.
5. An adventure on the river Nile
The Nile: imagine the romance of sailing on the tranquil waters, in contrast to the extraordinary tombs, monuments and temples revealed along the mighty river's banks, a combination of indolent relaxation and high-pitched exploration. Whether the Egypt of your imaginings is inspired by Indiana Jones, Agatha Christie or indeed Antony and Cleopatra, you're not going to be disappointed.
6. Straddling continents in Istanbul
Byzantium, Constantinople or Istanbul, this is an extraordinary city both Asian and European, a vibrant meeting of two continents. Arriving from the Mediterranean or the Black Sea, you will end up in the tranquil Sea of Marmara, crowded with boats and ships of all shapes, sizes and nationalities, and overlooked by the flattened dome and elegant minarets of the Blue Mosque.
7. Sailing under Tower Bridge
Imagine how it would be to sail into the very heart of a city, following the wakes of ancient mariners. There are a few appealing options - Sydney, for example, or Hong Kong - but what could be more iconic than sailing up the Thames into London, passing the gracious Royal Naval College at Greenwich, and finally watching the lifting of the bascules as you pass into the Pool of London, to tie up opposite the Tower itself.