In 2013, the world marvelled at Emirates Team New Zealand and Oracle Team USA flying above the water in the 34th America's Cup.
A spectacular introduction to foiling for most people, it sparked a sailing revolution.
Since then foils have been added not just to yachts but to every form of board imaginable - and their popularity shows no sign of waning.
Wherever there are waves or wind you'll find foilers this summer - and a crowd of onlookers taking in the spectacle.
If you're thinking of joining them, or just wondering what the fuss is all about, here's what you need to know.
Like many watersports, foil-boarding has its roots in Hawaii.
Hydrofoils had been used with personal water craft since the early 1960s when the first foiling waterskis were patented.
But surfing legends like Laird Hamilton and Dave Kalama are popularly credited with pioneering the type of foiling popular today.
First seen being towed behind a boat standing on a foiling surfboard in the early 2000s, they then started getting tow-ins onto the massive waves Hawaii is famous for.
In New Zealand, experts agree the 2013 America's Cup threw foiling in front of the general public. Two years later kite-foiling began to take off.
The owner of Mt Maunganui's Assault Boardriding Centre, Glenn Bright, said before then hydrofoils were out of reach for most because of the price.
"The technology wasn't there to build them light enough, strong enough and make them affordable," he said.
Kiteboarding brands were the first to mass produce foils, and in the five years since they have been added to every board imaginable.
Last summer the sight of a lone person on a foil board with an inflatable handheld wing had the whole beach stopping to watch. This year you'll be hard pressed to find a beach without one.
Wing-foiling has only been around for about 18 months but is already touted as the next big thing.
"It's taken off worldwide," said Bright. "No one really saw it coming. Wing-foiling as a sport is going to explode."
Akin to windsurfing, but with a foil and without the mast, riders hold a lightweight inflatable wing in the direction they want to catch the wind while standing on their choice of board.
Bright started his business in 1992 and had never seen as much interest in one thing as he had in wing-foiling during 2020.
"It looks quite simple and unintimidating. [All the gear] fits in the back of your car. I've had people that have no boarding or sailing experience and within six to seven hours of practice they are achieving a good result."
Auckland's NZ Foil Centre owner Sam Loader agreed that kite-foiling was going to take a back seat, with wing-foiling set to "explode".
He ordered 120 kits at the start of spring and sold them in three weeks. In October alone he had taught about 30 people to wing-foil.
The sensation was like being on your own America's Cup boat and you could do it even in low winds.
"It's the perfect balance between adrenaline and fitness. It's highly addictive. It's kind of social too - anyone can do it," he said.
"It's so fun, so addictive. It makes days that aren't that surfable fun. It gets you in the ocean."
Despite the sport being new, Takapuna Yacht Club had a number of wing-foilers competing alongside kite- and wind-foilers in their Thursday night summer series, events manager Danika Mowlem said.
"Foiling is the direction sailors want to go in," she said. "You can't watch something like the America's Cup and then put kids in optimists [the smallest sailing dinghies]. Sailors just want to go faster now."
Olympic Gold medallist and America's Cup sailor Nathan Outteridge decided to try wing-foiling when Covid-19 halted international competition, keeping him at home in Auckland.
"The more you do it, the more addicted you become," he said.
"The first feeling you get is it's really smooth. If you've done surfing or wakeboarding you feel every bump, every wave. On a foil the sound just disappears, you glide. It's effortless and it's very low impact on the body."
But even one of the world's top sailors had plenty to learn.
"I rocked up as this guy at the beach who couldn't jibe or turn corners. I kept falling off and I think they thought I had no idea."
Despite being a helmsman on Artemis Racing and a skipper during the Challenger Series for the last America's Cup, Outteridge had to learn the physics of a fixed hydrofoil because foils on bigger boats were adjusted using computers.
Given the speed at which the sport was developing, Yachting NZ high performance manager Ian Stewart said he wouldn't be surprised to see an organised international wing-foiling event start soon.
THE COST: For a foil, board and one wing you'll be paying a minimum of $4000. To make the most of the summer two different-sized wings are recommended for different wind conditions.
Wind-foiling has rejuvenated the windsurfing community in New Zealand, according to Stewart.
The sport, which has been accepted as a class in the 2024 Paris Olympics, has essentially seen a hydrofoil added to the bottom of a windsurfing board, allowing them to go faster in lighter winds.
"We're seeing a shift in our sport and it's all come from the America's Cup in San Francisco."
Before the addition of wind-foiling to the Olympic line-up, Yachting NZ was down to two competitors in the old RS:X windsurfing class, Stewart said.
"It's instantly revived the class. Already we have the largest fleet of the Olympic classes," he said.
"A lot of the youth have come back and they see a really exciting pathway to the Olympics."
The main driver was that wind-foiling was "just good fun".
"It's fast, it's athletic. It's exciting racing."
Sailors from other classes were using wind- and wing-foils for cross-training.
"It's a no-brainer of a sport. It's fast, tactical and realistic in accessibility," he said. "It's making our sport much more attractive and interesting. It's a spectacle. It's opened it up to non-yachting interest."
THE COST: If you're already a windsurfer your standard sail will do the trick but a board and foil will set you back $3000-$4000. If you need a sail as well, you're looking at another $1000.
Kite-foiling was the first of the recreational water foiling sports and became popular in New Zealand about 2015, Bright said.
The lift riders can get by having the kite high above them makes it still arguably the most impressive of the foiling board sports to watch.
With kite-foilers able to operate in winds as low as 6 knots, few days were off-limits to experienced riders.
But the code was not as easy to pick up as wing-foiling and Bright did not recommend trying it unless you could already kite-surf.
"It's like trying to learn two sports at once," he said.
Kite-foiling too has earned a place in the 2024 Paris Olympics. In a mixed gender relay format, each member of the two-person team will take turns doing a lap of the course.
Part of Yachting NZ's high performance programme, Justina Kitchen and Lukas Walton-Keim are our top kite-foiling team and working towards qualifying for the Paris Games.
Kitchen was initially a competitive windsurfer but switched to kiteboarding when it replaced windsurfing at the Olympics.
She fell in love with the sport before the International Sailing Federation reinstated windsurfing.
Kitchen decided to give kite-foiling a try in 2018 after her husband bought a foil for the family and has been addicted ever since.
With top speeds of around 70km/h and an average of 50km/h, it's not for the faint-hearted.
"It's really fast. When you come out of the water it's silent - you don't have that slapping of waves. It's easy to come out of the water in a straight line but manoeuvring is quite difficult," she said.
"You get that sense of flying and the weightlessness and the silence. It's just so much fun."
And it's not just for young people, she said. One of the kite-foilers in their fleet was in his late 60s.
THE COST: If you already have a kite all you need to add is a board and foil which will cost about $2000-$2500. If you need a kite, harness, bar and line you're looking at another $1500 minimum.
Prone and SUP foiling
If you're more a surfer than a sailor, prone-foiling or stand-up paddle (SUP) foiling might be more for you.
It's also easier on your back pocket than the wind-driven versions.
Prone-foiling is a fancy name for regular surfing with a hydrofoil attached to the board.
SUP-foiling is much the same. As with a normal SUP, riders start in a standing position and use a paddle to propel them on to the waves.
The addition of a foil creates an additional challenge, allows riders to go faster and gets them into the water more often.
Even on days when the waves were too small or fat to surf normally, you could foil on them and have "an absolute ball", Bright said. "Those are the types of days when you usually wouldn't even go out."
THE COST: Adding a foil to an existing surf or SUP board will cost you about $2000. For a purpose-built prone-foiling set-up you're looking at $2500 up. while a SUP-foiling kit starts from about $3000.
But wait, there's more
Board foiling sports don't stop there.
You can try your hand at tow-foiling behind a boat if water skiing and wakeboarding are more your thing.
For an extra buzz there is tow-in foiling where surfers use a jetski to tow them onto waves too big to catch on their own.
Downwind SUP-foiling is another option. With a decent swell offshore, SUP riders can go for miles using the foil to ride from swell to swell.
For a non-stop workout try pump-foiling. Riders get a running start from the shore or a dock and then pump the board up and down with their legs to keep it moving around a flat body of water.
The opposite is the e-foil, a self-propelled foil board that lets you cruise around flat water and get the sense of flying with minimal effort. You're bound to see a couple of these this summer.