Is a releasable locator beacon (ELT) required for aircraft carrying passengers over a water area? Is an Emergency locator transmitter - ELT required on any type of aircraft carrying passengers over water? Does it need to be fitted with an hydrostatic release unit so that it doesn't sink with the aircraft?

If they don't carry a releasable ELT, how are aircraft planned to be located after an accident over the ocean?

References to regulatory documentation definitely a plus (e.g. for the US, or for island countries like Australia or New Zealand).
Is an ELT required on any type of aircraft carrying passengers over water? 


Generally, commercial transport aircraft are not required to carry an ELT.


  how are aircraft planned to be located after an accident over the ocean?



I believe pilots are expected to use radio to inform controllers of any emergency.
If ATC are unable to contact an aircraft for an extended time, they instigate S&amp;R based on the last known location of the aircraft.
The FDR and CVR are required to include an underwater location beacon (ULB), though this is only short range and has limited duration.
It is expected that, sometime in the future, commercial transport aircraft will be required to have automated systems that report their position frequently (perhaps every 15 minutes)




References:


IATA - Aircraft Tracking Task Force (ATTF)
ATTF FAQ
ICAO Normal Aircraft Tracking Implementation Initiative