August 29, 2011: The Singapore Navy has received the first of two refurbished Vaastergotland class submarines from Sweden. The refurb was really a rebuilding of the two boats, as their size was increased by a third. These 1,400 ton rebuilt boats are 60.5 meters (198.5 feet) long, carry a crew of 28 and are armed with six 533mm (21 inch) and three 400mm (15.75 inch) torpedo tubes. The 400mm torpedo is for other subs, while the larger torpedo is for surface ships. These tubes can also carry mines.

The two Swedish subs were sold to Singapore in 2005, and have spent the last six years being rebuilt and upgraded. For example, the boats now have air conditioning and other mods useful for subs spending all their time in tropical waters. In addition to new electronic systems, the boats have air-independent propulsion (AIP), which accounts for most of the added size. Surface speed is 15 kilometers an hour, while submerged speed is 28 kilometers an hour.

Four Vaastergotland class boats were built in the 1980s, and were succeeded by the Gotland class in the 1990s. This was the first submarine designed from the start to use AIP. The Gotland can remain submerged for 19 days and is among the quietest non-nuclear submarines in the world. The four Gotland class boats are highly automated, with a crew of 25. They displace 1,494 tons, are 61.3 meters (190 feet) long and have four 533mm torpedo tubes (with 12 torpedoes) and two 400mm tubes (with six torpedoes). The refurbished Vaastergotlands come very close to matching the Gotlands in performance.

The second of the refurbed subs will arrive next year. The two Vaastergotland class subs that remained in Swedish service received a similar upgrade, before Singapore bought the two other Vaastergotland boats.