YMS (abbreviation for Yard Minesweeper) is a term for a type of American base minesweepers from the Second World War. Units of this type entered service from the first half of 1942, and a total of 561 units of this type were created! The length of the ship of this type was 41.9 meters and a width of 7.5 meters. The displacement reached approx. 320 tons and the maximum speed - approx. 12-13 knots. The units had different armament variants, but very often they consisted of a single 76.2mm cannon, two 20mm Oerlikon cannons, and acoustic and contact mines.
YMS minesweepers were designed for mass production from the very beginning, which entailed their simplest construction. What's more, the units of this type were made of wood to a great extent, which on the one hand reduced production costs, and on the other hand - such a solution was a great solution for magnetic minesweeping. In the course of production, three main variants of the YMS minesweepers were created, differing in the number of chimneys, and so: the Mark I version had two chimneys, the Mk. II only one, and the Mk. III - did not have it at all. During World War II, units of this type served, among others, in the USA, Great Britain, the USSR or in the Navy of the Free French. After the end of hostilities, exactly in 1947, four units of this type were purchased by Poland. Three of them (ORP: Foka, Delfin and Mors) were handed over to the Navy, and one (Zodiak) became a hydrographic vessel.