Turin
The fix ELT on the 777 can be set off manually in the flight deck or by impact (G-switch) The aircraft also carrys 2 ( depending on airline this number) portable 406 MHz ELT. The are activated by water and located by the doors. The have a floatation material over it and an antenna. Unless it is manually release from its stowage it will not float to the surface like a bouy and transmit. so it will sink to the bottom. The CVR and FDR have an ultrasonic beacon bolted on each of the and they will transmit away underwater