Triggerfish sure can do some damage, if that is made by a triggerfish or something else entirely is hard to say, but it wouldn't surprise me if a big Titan Trigger could have done that to a plastic dome. They are evil animals!
This is a good question! As you can read in the previous posts everyone has made their own, often very different, experiences with carry on luggage.
I happen to work in a place where almost all of our guests bring heavy camera gear and this is what I can tell you:
1: Bringing underwater housings, domes, lenses, cameras is not a problem. Security might wan't to have an extra look at it because they don't know what it is. I have never heard of anyone being denied bringing their UW camera as a carry on because of having the items deemed "dangerous" or such.
2: More and more airlines have started weighing carry-ons. In fact today I had guests arrive, coming from the US with Singapore Airlines, they had to talk to the local airline manager to be allowed to bring the 13kg of carry on camera gear that they had with them. Max weight allowed was 7kg, but in the past they would never weigh the carry on.
It would be quite interesting to start a thread about which airlines weigh carry-on luggage on which stretches!
Since I never shot with the Vixia HF G20 myself it is hard for me to compare the two, they are completely different machines both capable of producing great quality video when in the hands of the right diver.
If you are going to Tulamben then you can't miss Seraya's Secret, just in front of Scuba Seraya, fantastic muck dive, I have dived it very regularly over a period of 5 years and it never disappoints! Bring a 100mm Macro.
Highlights at Seraya's Secret:
-Various tiny frogfish
-Both common and Pygmy Seahorses
-Lots of nudies
About 1km further North-west of there in front of a Temple there is another great muck site, the dive-site is called Melasti and since a few years there has been a sign on the side of the street pointing to the entry point. Bring a 60mm Macro.
Highlights at Melasti:
Rhinopias (they used to be at 32m, straight down from the middle of the small reef past the artificial reef)
Doto Sp (Donut Nudibranch)
Lots of Ribbon Eels, blue, yellow and black
Ornate Ghost Pipefish
Both divesites are 5min by car south-east of Tulamben, get a good guide to take you there and you will have a great time, enjoy!