Akka:

The Akka was a 2,200 ton Landing Craft (LST) of the Egyptian Navy which was sunk in the Suez Canal as a concrete filled block-ship in 1956. At 300 feet in length, the ship provided effective blocking of the canal 50-miles south of Port Said.

In the days leading up to the blocking of the canal, there were reports that the Egyptian Navy had intentionally prepared a number of ships as block-ships by filling them with rock and concrete, the Akka being one of them, others were rigged with explosives instead.
This photo is of the blocked entrance of the Suez Canal at Port Said.
Excerpt from CIA Intelligence Summary 01 November 1956:
"The Egyptian LST Akka, which Cairo declared to have been sunk in the Suez Canal near Lake Timsah by Anglo-French action, is believed to have been scuttled by the Egyptians in order to block the Suez Canal. An Egyptian LST loaded with rocks had been reported held in readiness in this area for such a purpose."

The French-Anglo forces must have been aware of the possibility of the Akka being used as a block-ship as indicated by this excerpt from the Naval War College Review (Autumn 2006, Vol. 59, No. 4):

Phase II of the air offensive (3 through 5 November) consisted of attacks on nonairfield military targets, such as stores, barracks, and military road and rail traffic south of Port Said. Of particular importance was the Gamil Bridge,which carried the only road linking Port Said with its hinterland. Because of poor intelligence (what was thought to be a swing bridge was actually a causeway for much of its length) twenty-seven bombing sorties were required to render it impassable (the British carriers were close enough to the target, however, to permit returning aircrews to advise changes in bombing technique). Heavy and accurate flak protected the bridge, causing the loss of one Wyvern. Destruction was finally achieved by a low-level "skip-bombing" attack by eight Seahawks, each carrying two five-hundred-pound bombs. High priority was also given to preventing the Egyptian blockship Akka, which was moored nearby, from obstructing the canal. Two attacks were unsuccessful, giving the Egyptians time to tow the ship into place and scuttle it, together with another forty-seven concrete filled ships, effectively closing the waterway.
This picture, taken on 10 Jan., shows the UN salvage vessels working on the wreck of the sunken Egyptian landing craft "Akka", which went down with a cargo of cement and is considered one of the most serious obstacles facing the UN fleet in the Suez Canal.
The raising of the Akka: (from a UN Salvage Team press release
One of the worst wrecks of all was the sunken landing ship Akka, a 300-foot long blockage lying straight across the canal 50 miles south of Port Said, filled with cement that had hardened to a solid mass of concrete.

Starting early in January, Danish, Dutch, and German vessels of the UN fleet worked laboriously on the Akka until mid-February, assisted by an Egyptian dredger.

As the wreck was lying on its starboard side, a pocket had to be dredged in the sand to help in the straighteningj job. Divers, hampered by strong currents in that part of the Canal, carried out preparatory work. Small "messenger wires" were placed under the sunken vessel so that larger lifting cables could be drawn through. The the Akka was lashed firmly between the twin lifting craft Energie and Ausdauer by means of 34 nine-inch cables under her hull -- new cables bought especially for the job at a cost of some $75,000.

When the ship had been straightened, the lifting craft were filled with water so that they sank almost to the Canal level; the cables attached to the wreck were pulled taut; and the water was expelled. As the lightened lifting craft rose like pontoons, the Akka -- a dead weight of 2,200 tons plus her load of cement -- rose with them.

Finally, with the lifting craft holding her encased in the web of cables, the Akka was towed 15 miles, at a mile-an-hour pace, to a dumping ground in Great Bitter Lake.

General Wheeler, watching the towing operation, commented, "A magnificent job." From New York, Secretary-General Hammarskjold cabled congratulations.
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