Growth investors know they need to be courageous every now and then if they want to get in on the next great growth stock. That often means buying a company that is being shunned by the markets or is trading at a premium valuation, both of which can make it difficult to hit the buy button.

So, what stocks could be worth the risk? We put that very question to a team of Fools, and they picked GoPro (GPRO 0.64%), SodaStream (SODA), and Glaukos (GKOS 1.70%).

A business man with stack of bills fanned out in hand

Image source: Getty Images.

A bold bet GoPro can be hot again

Travis Hoium (GoPro): It's not an easy time to be an investor in GoPro. The company is coming off a year that included a massive inventory writedown and a very poor launch for the Karma drone, which could have been a game-changing product for company. But the worst days may be over after the successful Hero 5 launch last fall, and bold investors willing to bet on a recovery could see huge gains. 

To adjust to its problems, GoPro cut operating costs by $200 million in the last year and pared down development to a few more focused products. The Fusion camera is one key upcoming product, a 360-degree camera that will take virtual reality and spherical images, and the software GoPro is using to stitch the images together will allow users to change the focal point in post-production. It will also work with GoPro's existing set of accessories. If the Fusion is a hit, it could push the company well past the breakeven non-GAAP results management expects in 2017. 

This is a bold pick because GoPro's future is very binary. If it can expand beyond the Hero line of cameras to the Fusion spherical camera and even an improved drone, it could be a big winner. But management needs to execute nearly flawlessly because the competition is strong in both of its new markets. DJI is the industry leader in drones while Samsung and Kodak are already making 360 cameras. Investors bullish on GoPro are making a bold bet that the company can translate its success in action cameras into these new markets.

Sparkling growth ahead

Demitri Kalogeropoulos (SodaStream): It takes a good dose of courage to buy a stock that's more than doubled in the past 12 months. But bold investors shouldn't let SodaStream's recent price spike deter them from this attractive business.

The at-home sparkling beverage machine producer is back in growth mode after pulling off a risky branding and strategic shift that moved its carbonation machines, marketing campaign, and retailing partnerships to a new focus around sparkling water over soda.

The change is working. Device sales jumped 37% last quarter even as increasing prices helped gross profit margin improve to 53% of sales from 51% a year ago.

Better yet, the company's aggressive cost-cutting in response to sharp sales declines in 2014 and 2015 left it with a far more efficient operation. SodaStream generated a record $44 million of net income last year even though its sales base had shrunk by 15% since its peak in 2013. As of last quarter, operating income is up to 13.8% of sales, trouncing the 7.9% result of a year ago. Meanwhile, Sodastream's base of engaged customers is growing at a healthy clip, with carbon dioxide canister refill sales rising 12% last quarter.

If you're worried about a potentially weak holiday season outing for its sparkling water machines this year, you might want to pass on this stock. On the other hand, investors comfortable with that risk will be tempted by its accelerating sales and profit growth in an industry that could see above-average growth for years.

I can see a bright future for this company

Brian Feroldi (Glaukos): Glaucoma is an eye disease that affects more than 4.5 million Americans and 83 million people around the world. Sadly, this irreversible condition tends to worsen over time, which is why glaucoma is the second-leading cause of blindness.

Glaukos is a medical device company that is hoping to make the future a little clearer for patients who suffer from glaucoma. The company innovated a miniature bypass stent that is placed inside the eye during cataract surgery. This device helps to restore the eye's natural fluid outflow, which helps to release intraocular pressure that builds up as a result of the disease. Glauko's data shows that releasing this pressure buildup with a stent greatly decreases a patient's need to use glaucoma medication.

Since its launch, patients and providers alike have rapidly adopted the iStent. So rapidly, in fact, that Glaukos' revenue has increased at least 40% year over since for 15 quarters in a row. Better yet, gross margin has expanded as its top line has grown, which has helped to turn the company profitable. With plenty of room left for expansion, Glaukos' future is looking up.

So why do I think you have to be a bold investor to buy shares? First, Glaukos is trading for more than 10 times sales, so the stock is very expensive. Second, there have been rumblings that Medicare is looking to cut the company's reimbursement rate, which, if true, could slow down growth.

While those risks shouldn't be ignored, I think that Glaukos has enough going for it to justify an investment. Still, potential investors should brace themselves for a bumpy ride.