Glavkos (Type 209/1100 & 1200) Submarine "S-113," Hellenic Submarines, https://users.otenet.gr
Greece's submarine fleet was imported exclusively from Germany's Howaldtswerke-Deutsche Werft (HDW), although with substantial technology transfer and domestic participation. Submarines are a visible aspect of the broader defense cooperation between the two countries: Greece is Germany's main recipient and Germany is Greece's main supplier of conventional arms.  The long history of HDW submarine exports to Greece seems to indicate little German concern over the arms build-up in the Aegean Sea. Both former and current coalition governments in Germany have willingly supplied Greece, despite arms export guidelines that theoretically prohibit the sale of weapons to countries in areas of tension. However, as Greece is a member of NATO, German governments might have found it difficult to explain to their Greek counterparts that they could not supply them with arms.
Greece was one of the first recipients of Germany's submarine exports, signing contracts for four Type 209/1100 submarines in 1967, and an additional four Type 209/1200 boats in 1975.  All eight of these submarines were constructed at HDW's shipyard in Kiel, Germany. However, when the Greek Navy decided to modernize the Type 209/1100 ships in the 1990s, Greece's largest shipyard, Hellenic Shipyards, completed the retrofit domestically under license from HDW. The Hellenic Shipyards, based in Skaramanga, provided a significant source of jobs in Greece and had been rescued from bankruptcy when they were bought by the state-owned Hellenic Industrial Development Bank in 1985. 
In 2000 and 2002, Greece ordered four new Type 214 submarines with air-independent propulsion (AIP) from Germany. Also in 2002, HDW and Ferrostaal AG jointly purchased the Hellenic shipyards.  The Greek yard received orders to license-produce three of the Type 214 vessels and to perform modernization on three Type 209/1200 submarines. Later, allegations would surface that Ferrostaal had paid bribes to the Greek government in order to ensure the Type 214 submarine purchase.  The third vessel of the Type 209/1200 class, the Okeanos, was refitted with an air-independent propulsion (AIP) system and recommissioned into the Navy in 2014. 
The first Type 214 unit, Papanikolis, was laid down at the HDW shipyard in 2001 and launched in 2004. However, the Hellenic Navy refused to pay the full costs of the Papanikolis after sea trials revealed a number of technical problems.  Although HDW retrofitted the boat to address these problems, the Greek government still would not accept it, and stopped its payments to HDW's parent company ThyssenKrupp Marine Systems (TKMS). This led to a lengthy contractual dispute between the two sides. In 2009, TKMS cancelled the contract for the Type 214 submarines, as well as the program for refurbishing two of Greece's Type 209/1200 units.  TKMS also threatened to shut down the Hellenic Shipyards, which would have cost thousands of jobs in Greece. However, in 2010 the two sides "reactivated" both programs and signed a new set of contracts whereby Greece would accept the four completed submarines and purchase an additional two Type 214 submarines instead of upgrading the remaining two Poseidon-class subs.  At the same time, TKMS sold 75.1% of its stake in Hellenic Shipyards to the holding company Abu Dhabi MAR. In May 2011, HDW pulled out of the agreement for the additional two Type 214 submarines due to payment concerns and allegations of corruption, leaving the fate of the program unclear.  By October 2014, only two Type 214 submarines had either been commissioned or entered sea trials, the Papanikolis and the Pipinos. 
To date, Greece has not taken any steps towards becoming a submarine exporter. HDW's purchase of Hellenic Shipyards initially opened the possibility for Greece to become a key export partner by marketing submarines produced in Greece with HDW-supplied material kits. However, after being sold to Abu Dhabi MAR, the Hellenic Shipyards would likely be unable to export the German technology. After the completion of the submarines for the Hellenic Navy, the shipyard may focus on surface ships or civilian boats.
 Paul Holtom et al., "Trends in International Arms Transfers, 2010," SIPRI Fact Sheet, March 2011, https://books.sipri.org.
 "Vertrage 1960-1080 [Contracts 1960-1980]," Howaldtswerke-Deutsche Werft, www.hdw.de.
 Mario Modiano, "Niarchos Agrees to Sell Shipyards to State Bank/Greek Shipowners' Deal with Hellenic Industrial Development Bank," The Times (London), 18 July 1985, www.lexisnexis.com.
 Michael Nitz, "Ferrostaal, HDW Finalise Hellenic Shipyards Buy," Jane's Defence Weekly, 20 February 2002, www.lexisnexis.com.
 "Germany's Thyssen to End Submarine joint Venture over Graft Claims," BBC Monitoring Europe – Political, 8 November 2011, www.lexisnexis.com.
 Theodore Valmas, "HS Okeanos Re-delivered to Hellenic Navy," Janes, 20 October 2014, www.janes.com.
 "Greek Inspectors Eye German Sub Deal," UPI, 28 March 2011, www.lexisnexis.com.
 Tim Fish, "Greece to Scrap Upgrades in Favour of New Type 209S," Jane's Defence Weekly, 4 March 2009, www.lexisnexis.com.
 "Submarine Forces, Greece," Jane's Underwater Warfare Systems, 2 November 2010; "Submarines' Programs," Hellenic Shipyards S.A., www.hellenic-shipyards.gr.
 "German Group Pulls Out of Greek Submarine Order: Minister," Agence France Presse, 16 May 16, 2011, www.lexisnexis.com; "HDW Cancels Contract with Greek Submarines," International Resource News, 25 May 2011, www.lexisnexis.com; "German HDW Cancels EUR 650m Order in Greece - Report," SeeNews Shipping, 24 May 2011, www.lexisnexis.com.
 "The Odyssey: Greece's U-214 Submarine Order," Defense Industry Daily, 8 October 2014, www.defenseindustrydaily.com.