Perhaps my remark about being puzzled was not sufficiently specific: I am familiar with the fact of RN personnel being used as ground troops on the Western fron in WWI as well as the examples quoted by Derrick.

My puzzlement was more why this version had chosen to change the protagonist to a sailor, but not to change the scene or manner of death. I would normally expect, in songs at least, sailors to be kileed in tempests or naval engagements, while battlefield deaths would be the preserve of soldiers. That would suggest to me that this would not be the original version, but a one-off variant.