I've had issues traveling with the camera body in the housing. A couple of times they have made me take it apart. Other issues, as many noted, are tool kits (a 2" mini-screwdriver is a problem, really???). I travle with quite a few strobes, and they really don't like those. Make sure they will fire. Waiting for the issues with Li-ion batteries to come up.
As mentioned, above, be sure to tape all ends of loose batteries for dive lights (better yet, buy a rechargeable light). Loose batteries can come into contact with metal and short out.
But I carry all of my high $ gear on with me, keeping within the "volume" measurements. Nothing worse than getting to a city, to go on a live-aboard, and find your gear is missing.
My family won't even go through security with me anymore, as my carry on is myriad of lenses, wires, strobes, regs, etc., all tightly packed. The biggest nightmare is when they want to "delayer it", and start pulling stuff out of my carefully packed bag. And it's a real pain if you're traveling through an airport that sees few divers. I'd freak, too, if I was running the scanner, if I say my own stuff and didn't know what it was!!!!