Weymouth & Portland · United Kingdom · Wreck

P-555

Torpedo tubes and a 3in gun on a submarine at 40 m

P-555 began as the American submarine USS S-24 and was scuttled off Portland Bill in 1947 for use as a sonar target. She lies upright with her conning tower about 36 m down, her deck just short of 40 m and the seabed alongside at 45 m. Four 21in bow torpedo tubes and a 3in anti-aircraft gun are still on her, and the wreck shows well on an echo-sounder because she sits bow to the east on flat ground.

Also known as USS S-24.

Where it is and how deep

Depths on a shared scale to 60 m (197 ft); dashed lines mark common certification limits.

50.5152° N, 2.5578° WPublished position for this site.

The dive

You descend the shotline to the conning tower at about 36 m, the highest point on the boat and where the shot is hooked. From there the general depth of the deck is just short of 40 m and the seabed falls away to 45 m alongside, so bottom time is short and the plan matters more than the exploring. She sits upright and bow to the east on a flat seabed, compact enough that one pass down a side and back covers most of her.

The features are the armament and the shape of the boat: four 21in bow torpedo tubes forward and a 3in anti-aircraft gun. Large shoals of fish usually hold over the wreck, and conger eels and crabs use the gaps in the structure. She was not a war loss but a sonar target, deliberately submerged after being returned to the US Navy, so there is no damage to read and the dive is about the submarine herself. The ascent goes back up the shot.

The wreck

Vessel: P-555 (ex-USS S-24)
Type: S-18-class submarine
Length: 67 m (220 ft)
Sunk: 1947
Cause: Deliberately scuttled off Portland Bill for use as a sonar target
Lies: Upright, bow to the east, conning tower about 36 m down, deck near 40 m, seabed at 45 m

P-555 began as the American submarine USS S-24, an S-18-class boat of 67 m. She was transferred to the Royal Navy in 1942 as HMS P.555, decommissioned in May 1944 and returned to the US Navy that December. She was then scuttled in the English Channel off Portland Bill for use as a sonar target in 1947; sources differ on whether that was 28 April or 25 August. She has stayed upright and largely whole on the bottom, which is why she is dived as a submarine rather than as wreckage.

Marine life and season

Reef fish swarms
Macro critters

Month-by-month season rating for P-555
Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Fair	Fair	Fair	Good	Good	Prime	Prime	Prime	Prime	Good	Fair	Fair

Season follows Weymouth & Portland: Sea temperature runs from about 7 °C in February to 17 °C in August; winter gales off the Atlantic rather than the cold are what stop the boats.