I’m sure these little creatures are in fact sandhoppers Talorchestia quoyana. They are a brownish grey colour which makes them quite hard to see on a stony beach. Their bodies, which are up to 14mm in length, are compressed from side to side like other amphipods. The one shown in the picture above was a specimen I took home in a film canister and photographed later by which time it had lost its brownish grey translucence and become opaque. They leap or jump when you try to pick them up hence their name sandhoppers. They bury themselves in the sand during the day and come out to feed at night. I suspect the rough surf at Oaro had washed them from their burrows into the sea where they became a feast for culls.
Here is a .pdf with good info on Sandhoppers