From the "sunrise" which represents the beginning, to the sea and marine imagery which represents the soldiers childhood home, nature as a living memory is a key theme of this poem
The "green-blue" represents the earth which is home, the "silver" fish are also memories of his father who was a fisherman, the "grey" pebbles represent the soldier's happy family life
The end of the poem is deeply existential where it is projected that the soldier reflects on honour and respect and whether life has any meaning if you are not respected by others