Blue Water Index, an atlas of naval fleets

Field notes

The atlas uses separate evidence axes for where a ship is based, which hull it may be, and what operational status is publicly documented. It also preserves aggregate, unnamed hull slots when public sources cannot identify a pennant, rather than filling gaps with invented precision. Coverage is deliberately non-comparable: the British scope includes patrol, mine-countermeasure, survey, specialist, and Royal Fleet Auxiliary vessels, while other national scopes exclude some of those categories.