inflimbo wouldn't it be possible to mount few floatable transmitters.
perhaps even relaying last known position.
Offshore helicopters in the British North Sea have had them for years. The ADELT (Automatically Deployable Emergency Locator Beacon) is mounted externally and can be activated by the crew or it will deploy on immersion in salt water. It's signal can be picked up by any satellite.
Unfortunately it can to be armed or disarmed by the crew; neccessary to avoid accidental discharges on the ground where people are.