His wife and other family members were by his bedside.
Police said the weapon had not yet been found and were asking witnesses to come forward.
Meanwhile, the police investigation continues.
Checkpoints were set up at the exits of Waihi yesterday for police to talk to holidaymakers as they left the area.
Police had also asked New Year's Eve partygoers to supply their festive photographs, in the hope they could identify the attacker.
"People often take snaps of New Year's Eve revellers and then think nothing more of them," Inspector Dana McDonald said.
"What we're after is images of people in and around Beach, Hinemoa and Ocean View Roads, the surf club, camping ground and Esplanade between 12.30am and 1.30am."
Mr McDonald said when the attack occurred, officers were moving on large numbers of mostly young people from the area around the surf club, the motor camp, Beach Rd and Ocean View Rd.
Waihi Beach's normal population is about 3000 but swelled to 16,000 over the festive period.
About 20 police staff were working on the investigation, with the likelihood of more officers being called over in coming days.
Mr McDonald appealed to the attacker to give himself up.
"We are also appealing to the offender and his associates...at this stage we have a man who is quite critically injured and we want him or his associates to come forward and help us out."
While investigators have a lot of information to work through that has already come in from the public they are still keen to hear from anyone who may have seen something happen around 25 Beach Rd around 1am on Tuesday morning.
"We're still very keen to hear from anyone who may have taken images on their cell-phones, i-pads, i-pods or other technology of people celebrating New Year's around the surf club, camping ground, Beach Rd, Hinemoa Rd and Oceanview Rd between 12.30-1.30am on that day."
"If you have such images we would like you to email them to Police along with your consent for us to use them to our investigation team at thames@police.govt.nz."
Mr McDonald said given the advantages of modern technology it wasn't inconceivable that with the public behind them, Police could identify through images provided from the public, the majority of people present in the area around the time of the attack.