Related Rule
Greece
Practice Relating to Rule 47. Attacks against Persons Hors de Combat
The Hellenic Navy’s International Law Manual (1995) states in its chapter on submarine warfare:
The aforementioned practice followed during the two World Wars by no means should be considered as sanctioning the exception of naval warfare from the rules of armed conflict. On the contrary, the fundamental principles of IHL treaties concerning the protection and respect of shipwrecked, wounded, sick [and those] hors de combat … must be considered applicable. 
Greece, International Law Manual, Hellenic Navy General Staff, Directorate A2, Division IV, 1995, Chapter 7, Part III, § 4.
The Hellenic Navy Regulations (1993), as amended, provides: “The Commander orders the cease of fire against an enemy ship which has lowered the flag and surrenders, after taking all necessary measures of instant action to ensure that the above act does not constitute perfidy.” 
Greece, Hellenic Navy Regulations (Part A), Presidential Decree 210/1993, as amended, Article 5325.