After the bell on Tuesday, dry bulk shipper DryShips (NASDAQ:DRYS) reported some bulky quarterly numbers, thanks in large part to a slew of asset sales. Even after backing out those items, operating income still came in at $67.1 million, more than six times higher than last year. Shares were up 13% the next day, before the virtual ink on the press release even had time to dry.

The bulk commodity shipper's fleet has expanded at a steady clip, boosting total voyage days by 17% through the end of June. That outpaces Genco Shipping & Trading's (NYSE:GNK) 10% lift in operating days, but falls short of Diana Shipping's 23% increase.

The bigger contributor to DryShips' operating gains has been the soaring Baltic Dry Index, which is a composite of the rates earned by various classes of dry bulk vessel. DryShips' average time-charter equivalent rate -- voyage revenue minus voyage costs, divided by voyage days -- has risen by 55% through the first half of the year. The volatility of freight rates is what renders this a highly cyclical stock.

Because of that cyclicality, I believe that DryShips lacks investment merit today. Furthermore, this outfit is more highly leveraged than Eagle Bulk Shipping (NASDAQ:EGLE) or Excel Maritime Carriers (NYSE:EXM), which provides a huge return on equity while the going is good. But DryShips' debt load will cut results harder on any downdraft in dry bulk rates.

Can the company sustain or push beyond present highs over the next year or two? Sure. But over several years, there's little visibility, and that gets back to the question of investment merit. If DryShips shareholders plan on jumping ship at the first sign of a reversal, that sounds more like a speculation than an investment to me.

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Fool contributor Toby Shute doesn't have a position in shares of any company mentioned. The Motley Fool's disclosure policy has its land legs.