Road users were put at risk by a 20-year-old “pratting about” shining a laser pen into the eyes of a motorist.
Kyle O’Connor of Thames Road in Grantham admitted causing a danger to road users with his actions.
O’Connor initially denied the offence in interview then threw the laser in Grantham Canal. However he made full admissions in a later interview.
Chris Pye-Smith, defending, said: “He is sorry about what he did.
O’Connor was sentenced to a six-month conditional discharge.
Chairman of the bench Peter Dolby told O’Connor: “If this was just you pratting around then it should just go away.”
He must also pay £85 of costs and a surcharge.