Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of shipper TBS International (Nasdaq: TBSI) were sinking fast today, shedding as much as 14% in intraday trading on heavier-than-average volume.

So what: Today's selling comes on the back of a hefty decline yesterday that followed the release of the company's fourth-quarter results. As of this writing, the two-day sell-off has the stock down nearly 30%. In its earnings release and year-end 10-K filing, the company raised concerns that the sorry state of the ocean freight market could put the company in position to be in default as soon as June 30.

Now what: I recently wrote that I'm sniffing around the dry-bulk shipping industry for potential bargain stocks. The downturn in shipping rates, increase in fleet sizes, and drop in ship valuations have put a lot of pressure on shipping stocks. Being a cyclical industry though, my take is that the downswing may be the best time to venture into the sector. Of course, as TBS' troubles remind us, the downturn also means very real stress for the companies involved. When the eventual upcycle does come, it won't help investors who put their money into companies that went bankrupt or had to resort to huge amounts of dilution to stay afloat.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.