USCGC Bittersweet (WLB 389) was a C or Iris-class 180-foot buoy tender of the United States Coast Guard.

Built by the Zenith Dredge Company of Duluth, Minnesota, the ship was laid down on 16 September 1943, and launched on 11 November 1943.

Based at Kodiak, she carried out numerous search and rescue operations, fought fires, delivered medical supplies, and enforced fishing laws.

Bittersweet was then stationed at Woods Hole, Massachusetts and used for ATON and icebreaking. In addition she took part in oil spill cleanup operations and also participated in the International Ice Patrol.

Bittersweet was decommissioned on 18 August 1997, and given to Estonia. Renamed Valvas, the ship served in the Estonian Border Guard until it was decommissioned in July 2014 and given to the Estonian Maritime Museum. It is to become a museum ship.

The Iris-class buoy tenders were constructed after the Mesquite-class buoy tenders. Bittersweet cost $926,769 to construct and had an overall length of 180 feet (55 m). It had a beam of 37 feet (11 m) and a draft of up to 12 feet (3.7 m) at the time of construction, although this was increased to 14 feet 7 inches (4.45 m) in 1966. It initially had a displacement of 935 long tons (950 t; 1,047 short tons); this was increased to 1,026 long tons (1,042 t; 1,149 short tons) in 1966. It was powered by one electric motor. This was connected up to two Westinghouse generators which were driven by two CooperBessemer GND-8 four-cycle diesel engines. It had a single screw.

The Iris-class buoy tenders had maximum sustained speeds of 13 knots (24 km/h; 15 mph), although this diminished to around 11.9 knots (22.0 km/h; 13.7 mph) in 1966. For economic and effective operation, it had to initially operate at 8.3 knots (15.4 km/h; 9.6 mph), although this increased to 8.5 knots (15.7 km/h; 9.8 mph) in 1966. The ship had a complement of six officers and seventy-four crew members in 1945; this decreased to two warrants, four officers, and forty-seven men in 1966. It was fitted with a SL1 radar system and QBE-3A sonar system in 1945. Its armament consisted of one 3"/50 caliber gun, two 20mm/80 guns, two Mousetraps, two depth charge tracks, and four Y-guns in 1945; these were removed in 1966.

• "Bittersweet" (PDF). United States Coast Guard. Archived from the original (PDF) on 27 September 2012.
• "U.S. Coast Guard 180-Foot Buoy Tenders" (PDF). National Park Service.

• Historic American Engineering Record (HAER) No. MA-152, "U.S. Coast Guard Cutter BITTERSWEET, Woods Hole, Barnstable County, MA", 5 data pages

59°27′11″N 24°44′09″E / 59.453151°N 24.735871°E / 59.453151; 24.735871