Not a true helmet fan/user (for windsurfing), now absolutely in favor to use some in windfoiling activity.
Which one to choose and why.
I see many Gath and F.W. ..

I use the Gath helmet as its a close fit around my head, no sticky out bits to catch the water in a tumble. It must be 6 years old and still fine. Good for keeping the sun off as well.

+1 for Gath. Been using surf helmet on foil for 2 years. After perforating ear drum using Ion helmet, floppy ear protection didn't stop water being forced into ear in catapult...

I use the WIP wiflex Pro ... very very light, made with hard foam.

I have a Ride Engine. It is made for very spherical heads though. My head is shaped more like the creature in the movie "Alien". Huge gaps between the side of the helmet and my head made it floppy. I used a clamp and heat gun. Fits perfect now. The trick is to get the thermoplastic temperature high enough for plastic deformation without affecting the interior foam. The other issue was the sharp edge around the ear cutout. Wind noise would get very loud in high winds. I cut small "V" notches along the edge to break up the air flow which helped. The helmet came with "ear flaps", but too hot in Texas.

Without having a retail shop to try a bunch of different brands (like a bicycle shop), it a crap shoot.

Definitely try helmets on if you can, and otherwise get one that you can return if it does not fit. I have a Gath and love the idea of the visor, but it has a pressure point in the back that makes it very uncomfortable, so I pretty much stopped using it. The one I'm using now was bought in a store.

I've switched from a Neil Pryde to a Beanie low-profile motorcycle helmet (www.seabreeze.com.au/forums/Windsurfing/General/Another-Helmet-Option). The Beanie is relatively long front to back which fits my head much better than the more spherical designs, and is available in a true XXL which the Gath, Bern, Thousand, WRSI and NRS aren't. The Beanie is available with ear protection but so far I haven't felt that I needed it.

I use a Mountain bike DH helmet with the mouthpiece cut off.
As it is big it protects my neck from whiplash. The helmet has a big surface and stops on the water. It doesn't let the head go back.

AND IT IS OF A BRIGHT COLOR SO THAT IF YOUR GEAR FLYES AWAY YOU CAN BE SPOTTED ON THE WATER.

Not a lot of choice available (only Ion and Garth) when I bought mine 3 years ago. The Garth fitted like a glove and was much better than the Ion.

I've started (and currently using) with a cheap bike helmet.
Still in the low-mid 20ies vmax but now i feel more "in power" compared to my early days...
No longer ejecting when the things get rough, often with both feet in the footstraps, i already have experienced some nasty crash.
At my level i think the "freefall hook" should be my priority, closely followed by a combination of good impact vest (it seems Mystic has a foil model) and a Gath (Safety?)...

Bern Baker kayaking helmet. It has a little bill on the front to help keep the sun off my sunglasses.

Has anyone tried the Mystic MK8 helmet? Are the earpads any good?
I have an Ion helmet and the quality is terrible.

I've been using this one since starting to trying to do speed foiling...Tontron Helmet
www.amazon.com.au/dp/B08B8KSD95

protec snowboard or skate helmet. otherwise the WIP helmets look good.

Gath. It a good fit for my head. Lightweight. Watersport specific with a relatively long history of use.
Only other helmet under consideration is the Forward ProWIP 2.0. But would not purchase until I can test the fit.
Do not like heavy helmets. Friends use a ProTec model and NGR or NRG? Both are significantly too heavy.

Certified EU and USA skate and snowboard helmets might be an option. Designed for multiple hard impacts. Unlike cycling helmets. The Giro I use snowboarding is light. The Nutcase skate specific MIPs helmet used for esk8 is heavy relative to the Giro or Gath. MIPs adds a bit of mass.

As much as I would like a functional visor to block sunlight. Would avoid visors that can add enough drag to snap your neck back. The Gath seems to be designed to penetrate the water vs. catch the water. Something to consider for those higher speed crashes.

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OldGuy3 said..m The Gath seems to be designed to penetrate the water vs. catch the water. Something to consider for those higher speed crashes.

When I fall, I fall on my back. And as it is large (relatively :o) ) it stops on the surface. Ence, I don't want my helmet to penetrate the water but to stop at the same level to avoid backlash.

I use the Neil Pryde helmet with the carbon fibre look. Its a good helmet and has protected me in some gnarly crashes.

Gath, from www.naturalnecessity.com.au/ - signup up to the newsletter for 10% off I think.

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FranckG31 said..

OldGuy3 said..m The Gath seems to be designed to penetrate the water vs. catch the water. Something to consider for those higher speed crashes.

When I fall, I fall on my back. And as it is large (relatively :o) ) it stops on the surface. Ence, I don't want my helmet to penetrate the water but to stop at the same level to avoid backlash.

Windsurfing it seems like a significant number of my crashes end up more or less head first. Foiling. Hanging onto the boom for dear life during crashes seems to flip me over onto my side or back after the force rips the boom from my hands.

Pre-helmet era. Concussion and ambulance ride to the ER once. Don't remember much of that crash except "waking up" in the ER. Not a scratch on the body. People were guessing the skull decelerated faster than the brain. Helmet probably wouldn't have made much of a difference.

The Nico Prien crash at the last PWA event where he injured his neck. Helmet or no helmet the force of having your neck twisted, bent beyond normal range of movement when crashing at those speeds is a bit concerning. My foiling speeds (SS HG76 foil) are slow that it is probably not an issue. PWA racers. Helmet, impact vests, and maybe eventually a wind foiling specific designed neck brace?