High Quality Content by WIKIPEDIA articles! An udema (also udenma) was a type of warship built for the Swedish archipelago fleet in the late 18th and early 19th centuries. It was developed for warfare in the Archipelago Sea and along the coasts of Svealand and Finland against the Russian navy. The udema 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.