Mike Smith, a senior at Andrew High School in Tinley Park, said he bought the rotting boat for $90 and he and his friends spent about a month repairing the vessel and painting it black and yellow with thunderbolts to represent the school, the Chicago Tribune reported Wednesday.
Smith said he and his friends donned masks Thursday night and anchored the 12-foot boat in the pond in front of the school.
Principal Bob Nolting said he was initially concerned when the boat was discovered Friday morning, but his concern turned to appreciation when he read the note affixed to the stern.
"On behalf of the senior class of 2013, we hereby donate this boat as a token of our gratitude to our beloved high school," the note read. "We chose a safe 'prank,' which avoids any vandalism or obscenity and focuses on school pride to guarantee a non-offensive farewell. We have enjoyed our stay at Victor J. Andrew High School and we feel that our boat appropriately embodies the spirit of our entire class. We will truly miss this school and everybody in it. Thanks for everything."
Smith said the principal said he was impressed when Smith confessed to the prank Friday.
Nolting said the boat will be on display at the school's football field during Wednesday's graduation ceremony and he will then find a permanent place for the vessel.