S99: SAS Assegaai
The cache, a camo-taped preform tube, is hidden at this fine viewpoint off Dolphin Way which overlooks the SA Navy shipyard to the south-east where the large bulk of this black-painted submarine, is unusually fully and prominently visible, standing as it is on dry land.
The cache was originally prepared in recognition of SLAIN's GC4GV9J SA Navy View which was located not far away on Runciman Drive and archived in May 2014 after some 50 finds in its 8.5 months life. However, when preparing the listing, it turned out that the chosen location was too close to another cache at the Simon's Town library, so using Google Earth and Street View, I 'discovered' this promising alternative location which looked like it was well clear of other caches . . . I was well impressed with the reality - as you will be!
To reach the cache location: take Runciman Drive as 
far as S34 11.715 E18 26.000 and turn south here up the steep Nelson Drive. After 100m take the first right onto Horatio Way, then after a further 75m take the right turn off the tight left hand bend onto Victory Way. At S34 11.757 E18 26.003 take the right fork down onto Dolphin Way and continue 350m past a kramat on your left to the parking spot adjacent to a covered reservoir and opposite a small track heading down to the cache.
SAS Assegaai (S99) - ex SAS Johanna van der Merwe - is a Daphné-class submarine of the South African Navy. She is the only one of three of this type of submarine to remain - having been retained for preservation as a museum boat. The other two - SAS Spear S97, ex Maria van Riebeeck, SAS Umkhonto S98, ex Emily Hobhouse - were cut up and sold for scrap in 2003 and 2008 respectively. The Daphné-class submarines have since been replaced by the Type 209, or Heroine-class submarines.
History
On 10 February 1967, after nearly 2 years negotiation, an order was placed with the French Government to provide three Daphné-class submarines in addition to providing the training and infrastructure to run and maintain them.
S99 was laid down at the Dubigeon-Normandy shipyard in Nantes on 24 April 1969 and launched on 21 July 1970. Commissioned under command of Lt Cdr Theo Honiball on 27 August 1971, she completed workup training in the Mediterranean, operating out of Toulon, before sailing for home on 4 May 1972.
During the long passage, she was escorted by the frigate SAS President Steyn, and called at Cadiz, São Vicente, Luanda and Walvis Bay, before arriving in Simon's Town on 19 June 1972. Her arrival marked the successful culmination of five years of construction, trials and training to establish South Africa's first ever submarine capability.
It was not long before the submarines were involved in operations, and in 1975, just before Operation Savannah (Angola), 
S99 was deployed into Angolan waters under Operation Yskas to prepare for the evacuation of SA military personnel. During the South African Border War, she took part in clandestine special operations.
During her career, she underwent four refits, including installing additional fuel tanks, and the fitting of a locally developed RAKA combat suite in the 1980s, which replaced a cumbersome plotting table. In the late 1990s she received the SA-developed NICKLES fully integrated software based combat suite and two state of the art rebuilt periscopes.
With the acquisition of the new Type 209 submarines for the SA Navy, she was decommissioned on 23 November 2003 and subsequently converted into a museum ship as a part of the South African Naval Museum, through a project spearheaded by the SA Naval Heritage Trust.
More recently:
'SAS ASSEGAAI, the only submarine museum of its kind in Africa, was closed for tours and visits on the 3rd of August 2015. In the almost 5 years that the submarine was open to the 
public, as a museum, it drew in excess of 60,000 visitors, from 150 countries around the world. She was crewed by an eager group of volunteers and ex-Navy personnel and open to the public 7 days a week. For the sake of safety and preservation, it has however become necessary for urgent maintenance and repairs to be affected. She was successfully docked on the syncro-lift on the 2 September 2015. A feasibility study is currently underway for the proposed future placement of the SAS ASSEGAAI ashore, as a Museum. Regretfully and as a result, the ASSEGAAI will be closed to the public and tours until further notice'
See the S99 website for more information and great photos.
See here, here, here (cleaning the hull), here (walk through), here (overview) and here (paddle past) for short videos on the Assegaai.
Some facts:
Displacement, tons: 869 surfaced; 1,043 dived
Dimensions, feet (metres): 189,6 x 22,3 x 15,1 (57,8 x6,8 x4,6)
Main Machinery: Diesel-electric; 2 SEMT-Pielstick 12 PA4 V 185 diesels; 2,450 hp(m) (1.8 MW); 2 Jeumont Schneider alternators; 1.7 MW; 2 motors; 2,600 hp(m) (1.9 MW); 2 shafts
Speed, knots: 13.5 surfaced; 16 dived
Range, miles: 4,500 at 5kt snorting; 2,700 at 12,5kt surfaced
Complement: 47 (6 officers)
Torpedoes: 12 x 21.7 in (550 mm) (8 bow, 4 stern) tubes; ECAN E15 dual purpose; passive homing to 12 km (6.6 nm)
Countermeasures: ESM; ARUD; radar warning upgraded by Grinaker Electronics
Weapons Control: Trivetts-UEC weapon control system; DCSC-2 being fitted
Radars: Surface search; Thomson-CSF Calypso II; I-band.
Sonar: Thomson Sintra DUUX2; hull-mounted; active/passive search and attack; 8.4 kHz active. Thomson Sintra DUUX2 or UEC; passive range finding. Thomson Sintra DSUV2 or UEC; passive search; medium frequency.
Modernisation: Late 1990: weapon systems upgrading (including sonar), as well as improved habitability as part of a mid-life improvement programme. 19 May 1999: completed a 4-year refit and rejoined the fleet.