2 answers: Tenifer (unless it has changed) is still EPA non-approved. There are a couple of compaines that will do nitride finishing-Tenifer with a different formulary- here in the US, for about $250/whole gun-aftermarket, no US manufacturers use it. The best thing you could do to your Glock would be a Teflon coat over the Tenifer/parkerizing. I've done 3 this way, and it is superb. (DIY in the oven, for $42, including a new firing pin channel liner)
Travel in the open water is a crap shoot- arms are essentially illegal everywhere but US coastal waters. You might also run into trouble, depending on where you dock- NJ, for example. I don't know if the ports/bay rules are different than the municipalities, but something to check into. Personally, I would not travel by boat unarmed. PRA(
Personal
Risk
Assessment), though.
Edit to add:
www.glockmeister.com sells Glock parts, and Capital City Firearms (
http://www.ccfa.com/ ) is/will be selling aluminum, stainless and titamiun Glock frames @ +/- $299. If I were getting a new Glock, I'd order a stainless frame, and a complete top-end from Glockmeister. You're still in the $450-500 range of a poly-framed model. Purely a plug-n-play affair.