Polar cooler, 24 pack works great for me with a D7000 in Nauticam housing, Inon strobes attached (folded) plus nauticam 180 viewfinder attached. The cooler top stays open, unzipped. Put a longer strap with buckle through the loop handles, put the strap over my shoulder and carry the bag hanging from one shoulder on the way to the boat. If the boat does not have a good rinse tank for your housing, have them fill the cooler with fresh water before leaving the dock. Fill in on the boat if possible as it gets heavy. Then you have your personal rinse tank.
You can compress the cooler to a pretty flat size for packing in the checked dive roller for airline travel. Double it over, kneel on it to compress it and stuff in in the bag as the last thing into the dive bag then zip for heading to the airport.
Been doing this for over a decade with the same bag.
When the day's diving is done, it works as place for cold beverages as well.
Its great for shore based dive trips to/from the boat.