You wouldn't think there'd be many undiscovered plays on energy, what with the boom we've seen in energy markets (and stocks) over the past couple of years. Yet for all the talk about producers like ExxonMobil (NYSE:XOM) and Apache (NYSE:APA), or service providers like Transocean (NYSE:RIG) and Halliburton (NYSE:HAL), you hear relatively little about construction and engineering providers like Acergy (NASDAQ:ACGY), a company once known as Stolt Offshore.

The good news at Acergy is twofold. First, a recovery from troubles caused largely by bad contracts is now more or less complete. Second, energy producers are increasingly moving offshore to find oil and gas, which means that they need to build pipelines, platforms, and other subsea structures. As you might suspect, that's meant more work for the likes of Acergy, McDermott (NYSE:MDR), OceaneeringInternational (NYSE:OII), and others in that sector.

And this was a strong quarter for Acergy. Revenue jumped 55%, gross profit margin improved, and operating income was up about 80%, all while backlog climbed more than 40%. Between recent contract announcements from the likes of ExxonMobil and Chevron, and current bookings for projects stretching past 2010, it seems there's definitely good demand in the industry right now.

Yet I actually decided to take my profits and sell my Acergy shares. Willing as I was to play the recovery part of the cycle, I just didn't want to stick around for the rest of the story. In this industry, history has shown that margins are often bad, and economic profits are hard to come by. Perhaps this time will be different -- you could certainly argue that the stock is priced that way -- but I saw very little reason to press my luck when I had a fat gain already in hand.

By all means, the fundamentals of Acergy's business seem compelling -- more companies going offshore for oil and gas should mean more demand for these services -- and I won't argue with investors who want to stick by this stock. So instead I'll offer up this trite-but-true fortune-cookie aphorism: You don't go broke taking a nice profit.

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Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).