The Navy would have PRIMARILY issued 1 of 2 knives, although many others could have been, and were, issued.
The would have been issued either USN MK2s/USMC 1219C2s (same knife, different only in markings) or USN MK1s.
The MK2s are the 7" blade knives that frequently get called "kabars", although they were made by Camillus, Robeson-ShurEdge and PAL, as well as Union Cutlery (aka KABAR).
The MK1s are 5" blade knives and were manufacture by Camillus, Union Cutlery, PAL, Boker, Geneva Forge, Colonial, Robeson-ShurEdge (their No. 20).
They could have issued any type of 4" to 6" fixed blade during the first 2 years as the government requested that civilians donate any spare hunting knives they had to the war effort.
A sailor could also have acquired any of the "official" 6" knives that the army had made - the Cattaraugus 225Q, the Case XX 337Q6, the PAL RH36 an others.
On a sub, the most likely candidate would have been the MK1s. Any sub is short on space. WW2 subs were even more cramped than modern subs, and shorter knives would have been the "logical" choice, but in reality, it could have been almost anything, including 1920 vintage Marbles Ideals or ......
