In this segment of the Motley Fool Money podcast, host Chris Hill, Million Dollar Portfolio's Jason Moser and Matt Argersinger, and Total Income's Ron Gross talk about the companies they're most intrigued by this week and why: leisure company Carnival Cruise (NYSE:CCL), health insurance giant UnitedHealth (NYSE:UNH), and bitcoin and blockchain backer Riot Blockchain (NASDAQ:RIOT).

A full transcript follows the video.

This video was recorded on Dec. 15, 2017.

Chris Hill: Let's get to the stocks on our radar. Ron Gross, what are you looking at this week?

Ron Gross: I'm going to go with Carnival Cruise, CCL. They have a 48% market share. It's really an oligopoly type industry, really only a few major players because there's such high barriers to entry, Royal Caribbean and Norwegian being the other two folks. There's some favorable demographics going on here. We have an aging population. That should bode well for cruises. They have a solid balance sheet and proven financials and rates of return. 2.7% dividend yield, which we like over at Total Income. And, I think the stock has some nice upside potential.

Hill: All right. Jason Moser, what about you?

Jason Moser: Sure. You know I think healthcare is a phenomenal long-term opportunity there from a number of perspectives. Listeners have heard me talk about Teladoc a lot here in the last couple of years. I'm not pitching Teladoc today, Chris, it's something else entirely, it's UnitedHealth Group, UNH, going the other direction. Instead of a smaller player, this is basically the biggest dog in the space, and this is a big national healthcare insurer that runs the business in the UnitedHealthcare segment and the Optum segment for benefits and services. I think, regardless of how healthcare legislation shakes out, UnitedHealthcare is going to be part of the process there. They have vast amounts of data and information already on file. They're calling for earnings per share around $10.15 in 2018, which puts the stock around 21X full-year estimates. I don't think that's unreasonable for a company that's clearly going to take part in dictating this space for many years to come.

Hill: Matt Argersinger, what are you looking at?

Matt Argersinger: Let's see if I can get through this. [laughs] The stock on my radar is a little company called Riot Blockchain, ticker RIOT. Up until about a year ago, this was a penny stock biotech company. They actually had to undergo a one-to-eight reverse stock split in 2016 just to prevent themselves from being delisted.

Moser: Keep going.

Argersinger: Fortunately, earlier this year, in addition to changing their name to Riot Blockchain, they announced they were giving up on their biotech failure and instead were going to "gain exposure to the blockchain ecosystem through targeted investments in the sector with a primary focus on the Bitcoin and Ethereum blockchains." Since that announcement, in the space of about four months, the stock is up from about $3 to $28. I just have one thing to say: folks, be careful out there. Happy holidays!