Nice undress blue (working blue ) jumper! It appears to be in great shape.
On most WW2 ships, you did your own laundry by hand in a wash bucket. The holes in the bottom hem were for attaching "clothes stops", a short length of white cotton cord used to tie the just washed article to a clothes line for drying. As the war progressed, shipboard laundries became more and more prevelant.
Is that a draw cord in the hem? It is a pre-war feature that was still around during the war.