 The Una-class featured a single-hulled design, measuring 18.82 m (61 ft 9 in) in length with an average draught of 2.4 m (7 ft 10 in). The boats displaced 76.1 tonnes (74.9 long tons) when surfaced and 87.6 tonnes (86.2 long tons) when submerged. Because deploying naval commandos was one of their main tasks, they were equipped with an underwater exit / re-entry chamber.
