I have an innercom system from Racing Electronics that works pretty good. Is uses a small amp box with a 9 volt battery, that your head phones plug into. It is push to talk. When you want to talk to your buddy, just push the button. It is set up for a scanner, but I use my phone and plug it into the 1/8 jack and we listen to the IPOD music, and then just push to talk, it mutes the music. You can hear fine and you get about 12 hours of music listening/and moderate talking. Everything I needed came in the box, it was about $300.00 total cost about a year ago, including 2 headsets with mic, the amp box, and a cord to plug into my Phone/IPOD.
If you talk to Racing Electronics and tell them it is for an Airboat, you can have them delete the scanner and get the price near the $300.00
Another option is a setup by Simpson that uses Family Radio's and head sets. In that setup, you are not wired to the boat, and can walk around and still have the communication. Perhaps someone with that set up will chime in.
Here is the link to the Racing Electronics Website - this one includes the scanner that you won't need.http://www.racingelectronics.net/index. ... C-GEMINI-4