Wikipedia
A turuma (from the Finnish word "Turunmaa") was a type of warship built for the Swedish archipelago fleet in the late 18th century. It was specifically developed for warfare in the Archipelago Sea and along the coasts of Svealand and Finland. The turuma was designed by the prolific naval architect Fredrik Henrik af Chapman for use in an area of mostly shallow waters and groups of islands and islets that extend from Stockholm all the way to the Gulf of Finland.
It was designed to replace the galleys that made up the core of the fleets that operated along the coasts and in the archipelagos of the Baltic Sea. The turuma had a bigger draft, was somewhat slower under oars, but offered superior accommodation for its crew, was more seaworthy and had roughly ten times the number of heavy guns. It could be propelled with either sails or oars and was both smaller and more manoeuvrable than most sailing warships which made it suitable for operations in shallow, confined waters.
Between 1761 and 1790, 14-15 turumas were built, including Amphion, a modified version used by King Gustav III as both a pleasure craft and command ship. The turuma was among the heaviest in the arsenal of the archipelago fleet and a number of them served in the Russo-Swedish War of 1788–90. It had three masts, two decks and was equipped with 16–22 pairs of oars along with a crew of about 220–260. Its length was 35–39 m, width 9 m and the draft 3,3 m. The armament consisted of 24–28 heavy guns with up to 24 swivel guns for close-quarter combat.