Tuilagi, 20, swam to a nearby pier at the Auckland Ferry Terminal where he was met by police at 1848 local time (0648 BST) and taken to Auckland Central Police station.
The Leicester centre was given a pre-charge warning for disorderly behaviour before being released back to the England team management.
Tuilagi's fine will be paid to the Rugby World Cup's Christchurch appeal.
England manager Martin Johnson said: "This was an irresponsible thing to do. Manu has been disciplined internally and I have warned him about his future conduct."
Neither the police nor the RFU would confirm whether Tuilagi was drunk at the time he jumped from the ferry, shortly before it berthed on the Auckland waterfront.
It has been reported that Tuilagi was returning from a day trip with to Waiheke Island with fellow England team-mates.
"I'm really sorry. It was a silly thing to do and I apologise to everybody for any inconvenience caused," Tuilagi said.
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