Sherman thought he was sending an SOS signal to the world by activating an "epirb" -- short for emergency position indicating radiobeacon -- which is a satellite-connecting beacon that resembles a floatable walkie-talkie.

CNN: Shipwreck survivor recounts drama on high seas

The three fishermen's vessel didn't have an Emergency Position Indicating Radio Beacon, which transmits a distress signal anywhere in the world through a satellite system, the navy said.

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