Stanley Duncan, the chief executive of the DVA who had worked in the Northern Ireland Civil Service for 36 years, was fishing when Tuesday's fall happened.
Family friend David Farrell, who has spoken with Mr Duncan's wife and daughters, paid a moving tribute to him.
"I've known Stanley for all my life," he said.
"He was a great person for coming alongside you and encouraging you. He was honest, had integrity. He was a first class individual who will be sorely missed by us all."
He added that the Duncan family are "taking great comfort in the fact that Stanley had his faith".
Stanley was a great friend with a great sense of humour.
David Farrell, family friend
Environment Minister Alex Attwood was also among those who expressed sorrow over the tragedy, adding that colleagues were shocked by what had happened.
"I wish to express on behalf of myself, the DOE and wider Government, our sympathy to his wife, daughters, parents and family at Stanley's death in such tragic circumstances," he said.
"I have worked with Stanley Duncan for the last two years and he was well known to my Assembly colleagues."
Mr Duncan was recovered from the water near Victoria Terrace and taken to Causeway Hospital where he died on Tuesday evening.
Portrush RNLI and crews from Coleraine Coastguard were involved in the operation, alongside an Irish Coastguard helicopter.
Mayor of Coleraine Samuel Cole said it was a very sad time for the Duncan family.
"I'm devastated to hear the terrible news of somebody that was so well known in Coleraine County Hall," he said.
"I want to send my most heartfelt condolences to the family circle. It's a very sad time for them.
"The people of Coleraine will be devastated to hear this terrible news at this particular time."
He will be greatly missed.
Environment Minister Alex Attwood
Gary Young from Belfast Coastguard said: "It appears this man had been fishing from the rocks near Portstewart.
"Rocks can be dangerous and slippery so consider whether there is anywhere safer to fish. As there is little to hold onto, even a small wave can wash you off."
Police are continuing to investigate the death, but have said it is not being treated as suspicious.
SDLP MLA John Dallat said he was saddened by the death of Mr Duncan.
"As an Assembly Member, I dealt with Mr Duncan in his official capacity as Chief Executive of the Driver and Vehicle Agency on many occasions and I always found him to be a gentleman, thoroughly caring, professional and committed to the work he was doing," he said.
"His death is a reminder of the unpredictability of the sea and the potential dangers to those who enjoy it for recreational use."
Alliance Coleraine Councillor Yvonne Boyle also expressed her sympathy to the Duncan family.
"I would like to express my heartfelt sympathies to the family of Mr Duncan. This is an absolute tragedy which has shocked the local community," she said.
"I would urge everybody to be cautious if they are near the sea and take extra safety measures."