The Krischan der Große (lit. "Christian the Great"), also known by its misnomer Flusi 1 (short for “Flugsicherungsschiff 1”, lit. “Air traffic control ship No. 1”, due to confusion with an actual Luftwaffe ATC ship Krischan that is otherwise unrelated), was an experimental anti-air gunboat designed for the Luftwaffe in 1940, intended to be used as part of the planned invasion of the United Kingdom to provide anti-air cover for the invasion fleet. She was laid down in autumn 1940 at Rotterdamsche Droogdok in occupied Rotterdam and launched a year later. When the boat was commissioned on 19 November 1942, the Luftwaffe quickly found out its critical flaw: due to the boat’s compact design, the 88 mm Flak cannon was unable to elevate further than 8 degrees, effectively defeating the intended purpose as a floating AA platform. Because of this, the Luftwaffe cancelled the program and the sole prototype was kept to provide air cover via secondary light AA guns. Krischan de Große was later sunk on 24 February 1944 by a British air raid while docked in Amsterdam.

Introduced in Update "Winged Lions", Krischan der Große is a small, relatively slow, yet heavily armed gunboat. Featuring the 88 mm Flak cannon on the bow and a pair of quadruple 20 mm AA gun mounts, the boat has a variety of tools to deal with most targets it could face, with the 20 mm guns in particular being more than capable of shredding any PT boat into pieces. However, the boat’s survivability is mediocre at best, as the wooden-hull construction is unable to endure hits from large-calibre guns and autocannons, and the boat is otherwise helpless against early destroyers and frigates that became a common sight.