Royal Marines will be stationed in inflatable boats along the length of the Boat Race course on Sunday to ensure the event is not disrupted by another protester, organisers have said.
Last year's race had to be halted when Trenton Oldfield swam into the path of the two crews and narrowly avoided being struck by an Oxford oar.
Boat Race executive director David Searle promised improved security along more than eight miles of Thames riverbank and warned against anyone taking to the water.
Mr Searle said: "We are taking additional measures this year and have reviewed all of our actions last year in detail. The Boat Race course is four and a quarter miles long so we have eight and a half miles of riverbank to manage and monitor.
"There will be an increased presence both on and off the water, including support from the Royal Marines, but as with any security plan I cannot disclose the exact details.
"What I would say to anybody thinking of disrupting the race is that it's unbelievably dangerous. You risk injuring yourself, the crews and the other people following the race. Nobody wants that to happen. This is just a sporting event."
Oldfield, who claimed to be protesting against elitism, was released from prison in December having served seven weeks of a six-month sentence after being found guilty of causing a public nuisance.
The Metropolitan Police Service contacted Oldfield by letter and on Twitter to establish whether he was planning any action this year, saying they were "keen to facilitate any peaceful protest".
In a statement, the police stressed they were not offering to organise a protest but to afford him the opportunity to exercise his "lawful rights without causing disruption or danger to themselves or others".
However, Oldfield told The Spectator that he would be nowhere near the Tideway on Sunday. "In spite of the Metropolitan Police's kind offer I'll probably have a ramble across the Cotswolds instead," he said.