He spent the next two hours floating in the ocean, watching the sunlight disappear.
Cave, who was wearing a lifejacket, clung to a personal locator beacon (PLB) during the ordeal.
It helped rescuers save his life.
The Lowe Corporation Rescue Helicopter crew used night-vision goggles to locate him after the Rescue Coordination Centre in Wellington picked up his beacon activation on Saturday night.
The 19-year-old from Hastings is now encouraging others to always carry a PLB when heading out to sea.
Emergency services have echoed that message and said Cave did everything right, including wearing a lifejacket and taking his PLB with him in what otherwise may "have been a fatality".
Despite the scare, Cave has no plans to give up on his beloved hobby and has even bought a new kayak.
"I actually won that new kayak with an auto bid [on Trade Me] around the same time I was sinking on Saturday night."
Cave and two mates set off in separate kayaks for the fishing expedition about 3.30pm last Saturday, from Tangoio Beach north of Napier.
The wind was blowing toward shore at the start of the trip but switched and began blowing out to sea, with fairly choppy conditions.
The group were a few kilometres out to sea when one of the friends decided it was getting unsafe and headed back in about 6pm.
Cave and his other mate followed soon afterwards.
Things were going fine at first but Cave began to fall behind and noticed "the back of my kayak was getting quite heavy".
He soon realised it was filling with water due to a leak.
He opted not to yell out to his closest mate, about 200m or 300m away, as his friend did not have a PLB of his own and Cave did not want to put him at risk.
"I kept paddling another five minutes or so really slowly. Then the bow of my kayak just raises."
He was tipped into the ocean and his kayak was too flooded to get back on.
"I was having no success and thought, ‘I’m in trouble’."
He abandoned the kayak and activated his personal locator beacon sometime around 7.30pm, spending the next two hours waiting for rescue as the sun went down.
He said he kept "relatively calm" during the ordeal but it was "quite scary" the longer he was in the water, particularly after nightfall.
"The longer it went on I was starting to think, ‘Are these guys coming?’ because I’d never used a PLB before, and never expected to, and was thinking, ‘Have I used it properly?’" he said.
"There was probably a half-an-hour period when I hadn’t seen any sign of the chopper that I started getting a bit freaked out."
Cave said he was not concerned about getting bitten by a shark despite catching one earlier that day and drifting further out to sea.
He said he was hugely relieved when he hopped on the Coastguard boat - albeit extremely cold - and was informed his two mates had made it to shore safely.
"I want to say a huge thanks to the Coastguard, the Rescue Coordination Centre in Wellington, and the police who were great as well," he said.
"I was just really thankful they came to pick me up because it would’ve been a pretty cold night in the ocean."
His boss also came out to the coast to support the rescue.
Cave later learned his GPS position was not initially picked up by the Rescue Coordination Centre due to his PLB antenna not being fully extended.
He said there were a few lessons from the ordeal, with the biggest being, "I’d never go out without a PLB - always carry a PLB with you."
That included having a personal locator beacon, having it registered with an emergency contact, telling someone where he was going and wearing a lifejacket.
"If he didn’t have the PLB we potentially would have spent hours and hours looking for him, and it could have been a fatality."
He said it was also great teamwork by all the partner agencies involved.
"At the end of the day it was a good result."
He said it was important anyone heading out to sea carried a PLB or similar emergency beacon with them - from kayakers to boaties.
"I cannot stress enough the importance of hiring a locator beacon and registering it, and telling someone where you are going – not to mention wearing lifejackets," he said.
"These three [friends] did all the right things and they are here to tell the tale because of it."
He said without a PLB it was very hard to locate someone out at sea.
"Out on the water - if you are a long way from shore - there is no real reference point.
"If we get a GPS location they are within 20m or 30m."
He said even if there was no GPS location, such as initially in the case of Cave, emergency services could still make inquiries to narrow down the search after a PLB activation.
Knox said you can buy a PLB online or in-store from any hunting and fishing shop, and you can also rent them.
"Do not solely rely on your phone."
Cave’s kayak washed up on Marine Parade on Monday near the aquarium and has been reunited with its owner.
