Police area commander Dave Gaskin said the pair was part of a group of 11 friends who got into trouble yesterday while kayaking on Lake Tekapo.
Gaskin told Television New Zealand it was "very, very lucky" that all 11 students didn't die after they were struck by strong winds that swamped their vessels and thrust them into the frigid lake water.
Rescuers described the survivors as suffering hypothermia and in some cases being incoherent.
The students were all attending Monash University in Melbourne, Australia, and were visiting New Zealand during a semester break.
Hollnsteiner's Facebook page said he had been living in Buffalo and was from Staten Island.
Monash University said in a statement that the college community was "deeply saddened" by the deaths and that it had sent a senior manager to New Zealand to assist the surviving students.