As the launching ship would be under the radar horizon of the target, a data link or similar solution that required a line-of-sight would not work.

[2] The Ship Martel work was later picked up for a submarine-launched anti-ship missile, a project known as CL.137 USGW (Under-Sea Guided Weapon).

[a] This consisted of a Sea Martel with modifications to allow it to fit into a normal 21-inch torpedo tube, using folding wings and fins.

Indian Ilyushin Il-38 maritime patrol aircraft were also equipped with the rocket-boosted version of the missile, carried on unusual side-fuselage pylons aft of each wing.

[8] Sea Eagle is powered by a licence-built, paraffin-fuelled Microturbo TRI 60 turbojet and cruises at speeds of Mach 0.85 (1,040 km/h, 645 mph) throughout its 110 kilometre (68 mile) plus range.

[citation needed] Once launched the Sea Eagle is completely autonomous, with the flight and target seeking completely controlled by the on-board computer system which functions according to programmable options covering a large set of cruise, search and attack options, including a simple, pre-programmed 'point and shoot' mode that allows it to be carried by basic aircraft without radar, using targeting information radioed to the pilot from external sources or even visually located by him, with the missile's short minimum range assisting this.

A twin-gyro attitude reference system, digital flight control computer and autopilot are used to give the missile an over-the-horizon capability.

A C-band radar altimeter allows the missile to fly at very low level, minimising the range at which a ship can detect it.

The missile is fitted with a powerful semi-armour-piercing warhead, with a high ratio of charge to total weight, encased in a tough metal alloy casing.

[citation needed] A variant of the missile, called Sea Eagle SL (also P5T), designed to be launched from boxes mounted on ships was tested.

[citation needed] An unbuilt air-launched, land attack version of Sea Eagle, using a similar nose radar and semi-armour-piercing warhead, was known as P4T.

A later proposed land attack variant which would have had an imaging infrared or millimetre wave radar seeker-head and a data link to allow the launch platform to update the missile in flight was studied around 1990; this version was dubbed "Golden Eagle" and would have had a penetrator warhead to allow attacks on land-based hardened targets.

[citation needed] A proposed update of Sea Eagle in the mid-1990s with a dual-band seeker and improved systems was abandoned on cost grounds.