The surgery took about 85 per cent of his little toe and 70 per cent of the neighbouring toe.
His mother Caroline said "It's just a horrible accident."
Oska, a keen soccer player, was upset he would miss his school's cross-country race today.
Gisborne District Council which owns the pontoon and boat ramp, said the pontoon would not be removed and a second one was planned for the other side of the ramp.
"It is my understanding that Oska caught his toes between the edge of the floating pontoon and one of the piles to which the pontoon is connected via a U-shaped metal retaining bracket.
"The tide and wave surges result in the pontoon sliding up and down the piles. The pontoon sections are also hinged to each other so they move independently when the wave surges come and go.
"It is my understanding that it is a fairly standard sort of design on pontoons and we are not aware of anything immediately that would be better."
An engineer would examine the structure to see that it was functioning properly and there were no operational or maintenance issues.