What happened

Shares of containership operator Seaspan (ATCO) are down nearly 12% as the clock ticks down in the final minutes of trading Tuesday.

So what

The question everyone is asking is: Why?

It's not an earnings report that's to blame. (Although Seaspan's most recent earnings were bad, that news came out more than a month ago.) Nor is it Wall Street's fault. (The last upgrades/downgrades news at Seaspan came out not long after earnings -- and it was an upgrade, from Citigroup).

The most recent news item involving Seaspan was the company's own press release, announcing that it has accepted delivery of a 14,000 TEU containership called the "YM Wind." But while spending money on a new ship in a down market for shipping may not seem like the brightest idea, Seaspan has already chartered out the Wind on a 10-year contract to Yang Ming Marine Transport Corp. It's also already sold and leased back the Wind in a deal generating $144 million in cash -- cash that Seaspan will use to pay its final purchase installment on the vessel -- so this deal doesn't appear to add any financial strain to Seaspan.

A cartoon stock chart falls through the floor.

Seaspan stock is down -- and it's a real headscratcher why. Image source: Getty Images.

Now what

When you get right down to it, I don't see any news that would explain why Seaspan stock is slumping on Tuesday. That just might mean Tuesday's slump -- with Seaspan stock down 11.2% as of 3:45 p.m. EDT -- is a buying opportunity for new investors. Nothing more, nothing less.