After shore dives in Monterey, I find that the housing has scattered sand particles on it that don't come off after a soak in fresh water. I also see a bit of sand on the O-ring, although there's no water in the housing itself. Not sure what's going on. I'm tempted to blow off the outside sand with a can of compressed air or CO2, or maybe even a hair dry with the heat turned off.
I put the housing with the camera inside in a 5-gallon bucket pre-filled with warm water on my way home from diving. Home Depot sells watertight lid attachments for buckets with a screw-on lid.
On a boat, I dunk my camera in the rinse bucket after a dive and then put it in a secure place if one exists. Unfortunately, the only dive boat in Monterey that had a dedicated camera table stopped running.