Generally, BC, reg set, mask and fins get packed into two backpacks and two carry ons, with room left over for other essential items.
Fins for me are a big issue - not to beat a dead horse here, but I have a minor limb deficiency that requires fins that I have slightly modified to fit correctly. If push comes to shove, I could wear a rental set of fins without issues, but would rather not, so fins for me are a "needs to make it there item" and as such I carry them on. If it looks like it will be an issue, I'll just check them in the big suitcase.
I have been in this discussion about 500 times.
If fins are "the big issue", by all means, carry them aboard. If you don't try and drag all your other worldly possessions as carry on, no flight attendant would give you any trouble. If they raise an eyebrow, explain your issue- they are essentially a prescription item.
Why, oh why do you feel the need to carry-on all the other stuff? I understand carrying on computers, possibly even a mask if it were prescription, but why drag the BC and the Reg Sets? Check them.
The trick about checked baggage is to tag it 3 different ways- add your own heavy duty routing and destination tags. Bags will follow you everywhere.
If you're worried about theft of SCUBA gear (like reg sets, BCs and such), it really doesn't happen. What very little baggage thievery that occurs, SCUBA gear is not high on anyone's list. I don't care how much you paid for it- the resale values is nil- especially when compared to the concealability of a reg set in a baggage handler's jump suit. It just doesn't happen.
Reg Sets are basically bulletproof from physical impact. Check them through.
Once you start traveling often from Louisiana farther than the Florida Keys, this will become crystal clear:
Travel lightly, carry only
what you have to, like your flippers.
