Mr Black’s warning came after Coastguard Wanaka Lakes was called out twice in two days to incidents involving tourists on Lake Wanaka.
On Thursday, a member of the public reported two people in a kayak without life jackets struggling to return to shore near the Edgewater Resort.
Despite eventually reaching the shore without assistance, the pair were found to be totally ill-equipped, Mr Black said.
"They had absolutely nothing with them and with the southerly coming through could have been in a lot more trouble."
The pair were given a fair "tonging" by Wanaka police, he said.
On Wednesday a South American couple were rescued from the middle of the lake after venturing offshore in a plastic dinghy with just a willow branch for a paddle and no life jackets.
It was only a matter of time before a drowning occurred, unless visitors were educated about the dangers of the lake, he said.
"We want visitors to have a safe and enjoyable time on our lakes and rivers.
"That means being aware of the conditions, always wearing life jackets and having the right boats and equipment," he said.
Mr Black said he would work with the Queenstown Lakes District Council to get the boat safety message across to visitors.
