Svalbard

The ship is the operation. Divers live aboard for a week or more and the plan is set the night before off the ice chart and the forecast rather than off a site list, with the vessel repositioning overnight and tenders going out to whatever the bay is actually offering. Two dives is a good day and weather regularly takes one of them away. Much of the value sits above the surface anyway: landings, bird cliffs and long hours on deck watching the coast go past.

Underwater the archipelago is more productive than most people expect. Fjord walls carry dense beds of sea stars, urchins, anemones and soft corals, and the shallows grow thick weed wherever the bottom is hard. Where glaciers and rivers discharge, the sediment is a fine flour that lifts at a single fin kick and is slow to settle, so one fjord can be sharp at one end and milky at the other. Glacier fronts are dived well clear of any active face, among grounded and drifting blocks.

Walrus are the centrepiece and the least controllable part of the trip. Encounters are shallow, usually on snorkel and in a small group, and they end when the animals lose interest. Norway has also been tightening its wildlife-approach rules, including minimum distances at haul-outs, so how close anyone gets is set by regulation and the guide rather than by what a group wants. Ice work is the other set piece, on the days the ship finds floes worth getting under. Both run with an armed bear watch, which shapes every landing.

Expedition diving asks for a particular kind of diver: someone who can manage heavy gear, thick gloves and near-freezing water without a guide alongside, and who will not resent a day that produces no diving at all. Task loading is the real difficulty rather than depth or current. It works for photographers after animals and ice instead of reef, and for anyone treating the diving as one strand of a polar voyage. It is a poor fit for divers who measure a trip by the number of dives logged.