Any time anyone on the tennis tour gets a chance to play games with Roger Federer, they've got to take it.
So that's what Jack Sock did in the Match for Africa 5 in San Jose on Monday night -- and it was marvellous.
Federer teamed up with Microsoft supremo Bill Gates for the second year in a row, facing Sock and morning TV host Savannah Guthrie for an exhibition night that reportedly raised $2.5 million for charity.
But in the singles match between Federer and Sock, the Swiss great was the centre of attention... so Sock took advantage.
The world No.1 held break point against his American opponent when the Jaws theme started playing over the speakers.
Enter Sock's quick thinking.
A sly point to the roof made Federer look up as if to check for a shark fin.
All the while, Sock served underhand to surprise -- and embarrass -- the 20-time grand slam champion in brilliant fashion.
Unfortunately for Sock, Federer went on to win that first set in a tiebreak and the match 7-6 (11-9) 6-4.
The doubles match had its moments, too, with Federer dropping to his knees at the net and still winning a stunning point: