A Royal Navy rating from RNAS Culdrose registered nearly twice the limit for alcohol in breath when he was tested by police.
Officers had seen Anthony Neil Swanborough in a car on the A30 and found him smelling of alcohol.
He told Truro magistrates he had not thought he had drunk too much to be safe driving.
Swanborough, 26, who is stationed at RNAS Culdrose in Helston, pleaded guilty to drink driving on August 31 at Redruth.
He told the police he had been drinking the previous evening until the early hours at the Twilight Zone in Redruth. He tested at 65 mcg.
He was fined £350 with £120 costs and surcharge and banned from driving for 18 months.
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