Operator alumni lists, specialist forums where people research a single trip for two years, photography groups, and the ship itself, which produces the community rather than presupposing it. This is the loosest pre-existing community in the catalog.

What exists is the alumni layer: people who sailed together and stayed in touch, and operator repeat-client lists that function as informal clubs. The ship rather than the boat, a landing, zodiacs, the expedition team, the Drake, the polar plunge, cabin category, the single supplement, a shakedown, the bridge as an open place.

April, May, September, and October are the repositioning shoulders when the polar programmes are dark, and they are the deepest booking months for the following season. November to March for the Antarctic season, which is absolute: the ships are elsewhere the rest of the year.

June to August for the high Arctic. The equatorial destinations run year-round with wet and dry season variation rather than closure.