I found this one on the surface in the background. It had been in the sun for a long time and was quite hot but still alive. I think it had been collected by modern hunter gathers and accidentally dropped where I found it. It is now hidden in some mangrove roots where I can check on it from time to time. In Cairns, they are grilled and eaten, unfortunately the aductor muscle is quite small. In PNG the shells are used to make lime which is used with the locals chew beetle nut.