None of us love bear markets. But there's one thing about this sort of investing environment that's actually very positive. Bear markets offer the opportunity to buy many great stocks for bargain prices. Declines this year have left a lot of companies trading at a discount in relation to earnings or sales. And certain stocks may look cheap considering future growth prospects.

Many players are languishing today, but the difficult times won't last forever. When the situation improves -- or even anticipates better days -- these stocks could take off. Let's take a look at three wildly undervalued stocks that could go parabolic.

1. Etsy

Etsy (ETSY -0.86%) made big gains during the earlier days of the pandemic: The e-commerce platform for handmade goods saw gross merchandise sales (GMS) soar by percentages in the triple digits. Today, macroeconomic factors like higher inflation are weighing on Etsy.

Still, on a currency neutral basis, Etsy managed 0.2% growth in its marketplace GMS in the third quarter. And, importantly, the company has kept most of the business it gained over the past couple of years. Etsy forecasts fourth-quarter consolidated GMS of as much as $4 billion -- up about 130% compared to the fourth quarter of 2019.

New customers continue to come: The Etsy marketplace won 6 million new buyers in the third quarter. Buyers usually stick around, too; habitual buyers made up almost half of GMS in the third quarter. Why do people return to Etsy? A big reason is the variety of unique items from around the world -- which they can shop from the comfort of their own armchairs.

As for valuation, Etsy is trading at 29 times forward earnings estimates. That's about half of its level earlier this year.

Etsy is holding up well during these difficult times. And there's reason to be optimistic about the future of its earnings -- and its share price.

2. Moderna

Investors bet on Moderna's (MRNA -0.58%) coronavirus vaccine early in the pandemic. And they won that bet: The stock climbed more than 400% in 2020. This year, though, Moderna shares have lost their spark. Investors are worried about future revenue, and the stock is heading for a 27% decline for 2022.

It's true that coronavirus vaccine revenue probably won't reach the $18 billion annual levels of this year or last year. But Moderna has given us some clues about the post-pandemic market -- and that vaccine still could be a winning product for the company over time.

It's also important to remember that Moderna isn't only a coronavirus vaccine company. Right now the biotech is studying three non-coronavirus candidates in phase 3 trials -- investigational vaccines for influenza, respiratory syncytial virus (RSV), and cytomegalovirus. Each represents a blockbuster opportunity.

If all goes well in phase 3, Moderna could soon bring these products to market. The company has said it's possible the flu and RSV candidates could launch in the next two to three years.

It's not as useful to look at traditional valuation methods for Moderna because the company's future depends on these potential products -- as well as the coronavirus vaccine, in a completely different market landscape.

But if the coronavirus vaccine or booster can maintain blockbuster status, and Moderna launches at least one other blockbuster in the next couple of years, the stock will look cheap today.

3. Carnival

Unlike the other two companies I've mentioned, Carnival's (CCL -0.42%) (CUK -0.55%) story soured during the worst of the pandemic. Health restrictions meant Carnival's ships couldn't sail. The situation was temporary, but it was enough to crush earnings -- and increase debt.

This year, Carnival stock has lost 52%. And the shares are trading for 1.1 times sales, compared to about 3 prior to the pandemic.

Brighter days may be on the horizon for the world's biggest cruise operator, though. For the first time since it restarted cruises, the company reported positive adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) in the third quarter.

Occupancy and revenue are on the rise. And the company said booking volume for future cruises is ahead of an already strong 2019 level.

Of course, Carnival still faces two big challenges today. First, rising interest rates weigh on the cost of variable-rate borrowings, which will mean more expenses for the company. Second, the higher-interest-rate environment could hurt demand for cruises in the near term; potential travelers who are paying more for essentials at home may have to watch their budgets.

Still, these problems are temporary. If Carnival can manage them and progressively take steps toward profitability, this beaten-down stock could take off.