Saltstraumen

The tide table is the schedule. The strait settles only for a short window either side of high and low water, four times a day, and each day's windows fall roughly an hour later than the last, so kit-up times march through the week and this morning's dawn dive becomes an afternoon one later on. Guides work backwards from the tables to fix those times, and being late costs the dive outright: the water starts moving again and there is nothing to do until the next window comes round.

Entries are mostly from the bank, a short walk down to water level and a drop onto rock scoured bare by the flow. Below, the ground is boulder, ledge and gravel, grooved along the line of the tide and dropping away rather than shelving out. Growth follows the water: filter feeders pile up where the flow delivers most and thin out in the sheltered corners, so you work in close against the rock rather than looking out into open water.

Even at slack there is water on the move, and the dive has a tempo. You work along the rock, tuck in behind boulders and keep the guide in sight, because the turn of the tide is not gradual. The same nutrient load that grows the invertebrate cover keeps the water green, so this is a close-focus, strobe-lit site rather than a wide-angle one. Between dives the strait is worth watching from the bridge above, where it draws sightseers who never get near the water.

It suits divers who do not mind a day dictated by a tide table, and who care more about cold-water invertebrates than bottom time. Photographers do well, since the subjects are static, close and lit by strobe regardless of the ambient light. It is a poor first cold-water trip and a poor choice for anyone wanting long unhurried dives, because the diving is short by design and everything else in the day is arranged around those few windows.