The Coast Guard's backbone are four "Mirna" class patrol boats built during the early 1980s. Their radar equipment was modernized in 2007 and stern anti-aircraft guns have been replaced with a hoist with semi-rigid-hulled inflatable boats in 2009-2012 to help in their intercepting duties. These aging patrol boats will be replaced in 2016-9 with 5 OOB-39 project ships currently under construction in Brodosplit shipyard, which is the first major modernization of Croatian Navy in a while. Construction of the first out of the projected 5 vessels was scheduled to start in 2007, however the international tender for the construction of 5 vessels was published only on April 24, 2013. The tender called for the acquisition of a total of 5 inshore patrol boats which are to be 43.5 meters long, with a displacement of roughly 220 tons and a maximum sustained speed of at least 28 knots. They will be armed with a 30mm Typhoon Weapon System stabilized remote weapon station and two 12.7mm heavy machine guns along with a MANPADS launcher. The order was placed with Brodosplit in April 2015 and the keel of the first ship was laid in September of the same year. As projected, the first vessel was to enter service in the beginning of 2017, the second and third in 2017, the fourth in 2018 and the last one in 2019. Units were projected to cost around 10 million euros, respectively. The first prototype ship, OOB-31 "Omiš" was commissioned by the Croatian Navy on 7 December 2018. Four additional ships are under construction at Brodosplit shipyard as of November 2020.