High Quality Content by WIKIPEDIA articles! The USCGC Blackthorn (WLB-391) was a 180-foot (55 m) sea going buoy tender (WLB) which sank in 1980 in a tragic collision near the Sunshine Skyway Bridge of Tampa Bay, resulting in 23 crew member fatalities. An Iris class vessel, she was built by Marine Ironworks and Shipbuilding Corporation in Duluth, Minnesota. Blackthorn`s preliminary design was completed by the United States Lighthouse Service and the final design was produced by Marine Iron and Shipbuilding Corporation in Duluth. On 21 May 1943 the keel was laid, she was launched on 20 July 1943 and commissioned on 27 March 1944. The original cost for the hull and machinery was $876,403.