This is one of a number of Roman copies of a Greek original. The bent left leg is reminiscent of the Doryphoros, and the boy leans on a pillar like an Ephesian Amazon. The twist of the body and the slope of the shoulders, however, are much more extreme that in those and other works of Polykleitos.
It is possible that the statue was a funerary monument to a young athlete. The character of the sculpture is very reflective, giving rise to its being named after the youth who gazed into the water at his own image.
There is a complementary mirror-image copy in the Nelson collection in Liverpool
Paris, Louvre 456-7
Lippold: Griechische Plastik, 165 (n.8), pl. 60.2
Lawrence: Classical Sculpture (1928), 213
Said to have been found in the delta region of Egypt