EPIRBs are used for maritime emergencies, where ELTs are used in aircraft applications and PLBs are used for personal use.
I'm pretty sure the terra fix is intend for use on land. You need the Aquafix but both appear to have the same specs except that the Aquafix comes with some sort of head mount (undoubtedly for if you are bobbing in the ocean).
From what I can see, the major difference between an EPIRB and a PLB is that the EPIRB has a longer battery life, is a little more robust, and is considered a must if you are going to be in an area that may take rescuers more than 24 hours to find you. PLBs are EPIRBs for not so remote areas, battery life under use is 24 hours. It would seem a marinized PLB should be sufficient for the job, but the real question is does it meet the stated requirements for the race.
