What to look for in a whitewater canoeing helmet

Wearability

The first consideration is get one that you will wear. If it's annoying to put on, or you're embarrassed to wear it and will be tempted to skip it, that's of no use to you. The best helmet in the world is not going to help you if it's not on your head. 

There are specialized whitewater canoeing helmets, but I'm of the opinion that its number one job is to protect your head from impacts. All of the features that make a helmet a whitewater helmet are trivial compared to its main job of impact dampening. This means that it's ok to use a multi-sport helmet, or a bicycle helmet as long as they fit well and a rock will hit it instead of your head. 

Fit

You want a nice snug fit that's still comfortable to wear. In this sport, you're not just dealing with gravity and your own speed, a rapid contains all kinds of forces in all directions. Imagine swimming through a large boil with water splashing up, to the sides and even up from the bottom. Your helmet needs to stay on your head for all of it and not shift around. To make sure it's good and tight, do the "rock star" test. Just thrash your head up and down like you're at a long haired heavy metal concert. Your helmet should stay perfectly in place throughout the test. 

Tighteners

Some helmets will have mechanisms for easy tightening. Some have a little dial to increase the tension, others have some little pinch looseners that allow the straps to loosen or tighten. These are just for convenience, especially switching from wearing something like a hat or a touque under your helmet. Then you can adjust on the fly to make more room. Manually adjusting the traps is more time consuming. This is something that can make a helmet quite a bit more expensive though. I had one that used rough plastic velcro as the tightener. I don't recommend that since it came loose all the time. 

Colour

I had a black helmet for many years and then I replaced it with a dark grey helmet - both dumb colours for a whitewater helmet. When you find yourself swimming in a rapid, often the only part of your body that's visible above the water is your head. It's in your best interest to make that part of yourself as easy to see as possible. Rescuers often need to track the position of the swimmers, and need an easy target to through a throw bag to. No need to give them an extra challenge by making yourself hard to see. Prefer 'high-viz' colours. My current helmet is the brightest fluorescent yellow I could find. 

Peak or no peak

Some helmets include a peak to keep the sun out of your eyes and some don't. I personally can't go without the peak, but it's possible to wear a baseball hat under a peakless helmet to add that protection. I think it also comes down to the kind of sunglasses you wear. My prescription is strong enough that they can't make wrap around sunglasses for me. Physics won't allow it. There's a certain hour in the late afternoon where the sun glares down into my eyes right over my sunglasses. I need that helmet peak to block that. If you have those sporty wrap around sunglasses, then you likely won't need a peak on your helmet at all. 

The peak can also add a bit of extra protection since it sticks out farther that your nose. Jacob nearly took a rock in the face underwater on one unfortunate run but the peak of his helmet took the blow instead of his face. 

Warmth

If you find yourself getting into cold whitewater paddling, which is especially the case for those chasing the big water in the spring, then you'll likely want a helmet that has some warmth features. Some have snap on ear covers that can help, but overall, your warmth won't come through the helmet, but from the neoprene that you're wearing under it. There are little neoprene paddling hats that are designed to fit under helmets.