Is this some kind of native plum? I couldn’t find the plant they came from, so maybe someone just dropped the fruit there. There were four of these scattered on the ground with no trees around that seem to have similar fruit. On grass next to the beach.
Resubmission of old observation with better photos.
On deck
About 2m long
They get fed with fish scraps.
A few of these on the compost tumbler
About 1.5cm in body length