Greetings,
Interesting & Involved project indeed. Looks like you are making some kind of wearable for swimmers. I have good expertise with BLE, GPS, Sensors, Circuit design, PCB design, embedded systems, rechargeable battery management. Please see my profile for details.
I have also worked on NEMA and IP rated enclosures in my previous companies - so I have experience with water tight enclosures.
I have recently finished a baby wearable involving BLE, PR and SpO2 monitoring, rechargeable battery with a running life of ~10days.
I think I can deliver this end to end to you. However it would be important to scope out the details and make it in a milestone based manner. This is my initial bid and will update as per our discussion.
Look forward to hear from you.
T & R
Alok Pugalia