"is there a contract between Dimitri and Big Bob's? If there is a contract, what type(s) of contract is (are)?

Jay's Flying Advertising, LLC, contracted with Big Bob's restaurant to fly an advertisement above the Connecticut beaches. The advertisement offered $5,000 to any person who could swim from the Connecticut beaches to Long Island across the Long Island Sound in less than a day. Frank Dimitri saw the streamer and accepted the challenge. He started his marathon swim that same day at 10 a.m. After he had been swimming for four hours and was about halfway avross the sound, Dimitri saw another plane pulling a streamer that read, "Big Bob's Burger revodes. "is there a contract between Dimitri and Big Bob's? If there is a contract, what type(s) of contract is (are) formed?"is there a contract between Dimitri and Big Bob's? If there is a contract, what type(s) of contract is (are)?
Was there an offer? Was there an "acceptance"? Was there "detrimental reliance"? Was the proposed activity legal? Was the attempted revocation effective? Would it make a difference if any of the unknown swimmers attempting to collect had been unable to see the second streamer along the beach 4 miles away where the offer was made? Would any form of revocation have been acceptable?