At least five people remain in hospital after breaking limbs during Oxford's traditional May Day bridge jump.
Police had warned revellers of the dangers of jumping
The police have criticised revellers who took part in the jump from Magdalen Bridge into the River Cherwell.
They estimate that about 12,000 people attended celebrations in the city centre on Sunday morning, which have been at the centre of safety concerns.
Oxfordshire Ambulance NHS Trust said they had to take 10 people to the JR2 hospital for emergency treatment.
Insp Justin Archer said: "I am extremely disappointed that so many people have ignored the advice issued by ourselves, the ambulance service and city council.
"With water levels at little more than knee-deep still people ignored warnings and jumped from the bridge, injuring themselves and others.
"Around half of those that jumped received injuries that required treatment from paramedics and I am sad to say that there have been a number of serious injuries, from badly broken legs and ankles, chest injuries, serious lacerations and even spinal injuries.
More than 100 people took part in the jump
"I only hope that some of these injuries will help educate people that what may seem just a harmless bit of fun could have profound effects on someone's health."
Every year thousands of people gather on and around the bridge to hear choristers sing hymns at dawn from the tower at Magdalen College.
But the authorities have been keen to stop people jumping off the bridge and Insp Archer warned Sunday's incident could have effects on the event as a whole.
The ambulance service's operational manager Adrian Fellows said: "All the casualties occurred in a very short space of time, putting pressure on this service and the hospital's Emergency Department.
"All of the injuries could have been avoided and even when those who were hurt were telling people still on the bridge not to jump, they continued to do so.
People had to be picked up from the river by boat
"Jumping into such a shallow river, which is also full of rubbish, is madness."
The bridge was closed during the celebrations for three years until 2001 after one young reveller was left paralysed.
In 2003, a handful of people jumped into the river after climbing over a two-metre security fence.
A year later safety barriers were erected and stewards stopped people from jumping into the river.
A spokesman for Thames Valley Police said there were no arrests this year and the bridge itself was clear of revellers by about 0700 BST.