Sure, the weather's a bit gloomy as I write from mercurial New England, but I promise I haven't suddenly gone Goth on you. Though I really am going to tell you about two small companies that profit from shipwrecks and dead bodies, my proffered investment advice today is figurative.

One of the things the Motley Fool Hidden Gems team seeks in an investment is dominant positioning in a profitable niche business. Sometimes, that means an unusual business, so you ought to keep an open mind when discovering companies that strike you as a little weird, smelly, or macabre. This niche idea goes a long way toward explaining why these two companies have absolutely stomped the market over the past five years.

Please note that I'm not recommending them for purchase today -- both stocks have moved up dramatically, and a lot of optimism is now priced in. But they do illustrate my broader point.

Stemm sells shekels from the sea floor
On Friday, I learned about a fascinating company that extracts riches from the ocean's depths -- but not in the same manner as offshore driller Transocean. Nope, this company literally finds money lying on the sea floor.

Odyssey Marine Exploration (AMEX:OMR) is a self-described shipwreck company that has potentially discovered the largest shipwreck treasure cache of all time. Reports place the total number of gold and silver coins recovered from this particular site at north of half a million. I hope none of my readers had casually bet against this quixotic little company either in CAPS or with real coin o' the realm, because the shares spiffy-popped upon news of the find. In other words, they rose by more than the amount investors paid for shares as recently as early April.

There were a few clues indicating that Odyssey Marine is no half-baked scheme. For starters, there were some successful people investing -- or perhaps speculating! -- here before Odyssey found its treasure. The top shareholder is GLG Partners, a London-based hedge fund whose principals are all ex-Goldman Sachs (NYSE:GS) folk. Fortress Investment Group (NYSE:FIG), which just recently had its IPO, is second in line.

More crucial is the profile of people involved. A professor of maritime law who has, in private practice, argued federal cases on shipwreck disputes sits on the board of directors.

Both Odyssey co-founders hold substantial personal stakes in the firm and have been plying their trade for decades. Most notably, one of them, Greg Stemm, has been conducting shipwreck excavations since 1986, and the United Nations has tapped him to weigh in on the Draft Convention for the Protection of Underwater Cultural Heritage. This fellow is no mere hobbyist, Fools.

Media coverage of the find was ambiguous regarding how Odyssey might monetize its newfound treasure trove. But this is where things get even more interesting. The company is emphatically not looking to cash in immediately. There's a separate marketing operation in place intended to maximize the lifetime value of the assets the company acquires. The coins will eventually be appraised, researched, and presented to collectors and investors as individual artifacts. This branding initiative will reportedly extend to TV specials and museum exhibitions.

Is the value of the reported discovery a sure thing? Certainly not. The Spanish government, for one, is up in arms, claiming that the company has no right to the wreck site's cultural artifacts. I don't know how this will turn out, but the company does appear to have the right lawyer.

Bodies in motion
Speaking of exhibitions, another oddball company is Premier Exhibitions (NASDAQ:PRXI), the operator behind extremely popular exhibits from the RMS Titanic and on human anatomy. Last July, Foolish colleague Ryan Fuhrmann noted that "Premier has obtained exclusive rights to recover objects from the Titanic wreckage off Newfoundland. These recoveries have spawned the related tours, licensing, and merchandise revenue." That's strikingly similar to Odyssey's operating model.

The Titanic business, however, seems to be heading toward an iceberg. Though it holds salvor-in-possession status with regard to the wreck site, Premier has been unable to prevent other operators from photographing and taking video recordings of the site. The company's legal claim to various artifacts recovered to date and its future status as sole salvor both seem to be tenuous over the long term.

Fortunately for Premier, the Titanic exhibits accounted for only 28% of last fiscal year's revenues. Now there's a new exhibit in town ... or, rather, all over the country and in select cities around the world. Premier has found a major hit with its quite graphic human-anatomy exhibits, billed Bodies ... The Exhibition and Bodies Revealed. Revenues have more than quadrupled since 2005, largely because of the popularity of these exhibits.

Premier has an interesting business model, so despite the challenges it may face in obtaining high-quality human cadavers -- legally, anyway -- I gave the company a thumbs-up in Motley Fool CAPS, the community-intelligence phenomenon that is sweeping Fool Nation. It's been my second-best pick ever, after fellow spiffy-popper aQuantive. Do I regret not picking up actual shares? I guess, kinda. But there are reasons to question the long-term investment merit (there is no other kind) of both Premier and Odyssey, as I hope I have made clear.

Diving deeper
At the outset of this piece, I mentioned the rubric that Tom Gardner and the rest of the Hidden Gems crew apply in their search for long-term small-cap winners. Odyssey Marine and Premier Exhibitions fit some of these criteria, but even though they sport solid insider ownership and operate in decidedly niche businesses, neither company has demonstrated the long-term, consistent profitability that typically earns a company a formal nod in the newsletter.

But don't despair. There are hundreds, perhaps thousands, of equally weird small companies out there, many with even brighter prospects. So dive in and see what's lying in the market's depths!

If you're not the solo voyager type, you can join the Hidden Gems community in its exploration of the small-cap market. The service offers up two stocks for your consideration every month.

Please don't email Fool contributor Toby Shute about cadaver purchase opportunities, but do write him with any other questions or comments. He doesn't own shares in any company mentioned. The Motley Fool has a disclosure policy.