I always wondered why you had to travel North to find and catch the delicacy we grew up with, the Blue Swimmer Crab (Portunus armatus).

Living on the coast in South Australia you have to travel thousands of kilometers to the west or to the east before you can start following the coastline heading north. This is not the kind of north I refer to. Fifty kilometers north up into the Gulf of St Vincent is enough to come across blue swimmers in their hundreds.

All these years later I think I have discovered their secret, the Blue Swimmer Crab is a tropical species that has become locally trapped here in the relatively warm waters of our Spencer and St Vincent gulfs.

So next time you see these intimating crabs on a cold water South Australian dive just imagine you are in the tropics and try and convince yourself it’s not so cold after all.

Photo: Robert Rath, ‘Blue Swimmer’, 1/160s f/13 ISO320 15mm