G’day Davie and others,
The super tough SPC906255 Spacecase (Spacecase Upside Down Box 900x620x550 mm - Spacepac Industries) is large enough for the BlueROV2 heavy configuration complete with payload skid and tether reel. The case is an up-side down style and the lid ‘just’ fits over the ROV when it it held in the right location (I used some spare pick-n-pluck foam for this). There is also plenty of height inside the case for packing or other light weight items above the ROV itself.
This case is manufactured down here in Australia however I am sure there are similar cases manufactured in other countries. It is big and strong however you probably won’t want to be flying with it.
For interest sake and to help with a sense of scale, that’s a Pelican Protector 1690 case sitting behind it on the floor.