Deep water is proving to be a lucrative place for drilling companies. Ships with the capability to drill farther and farther offshore are being built as quickly as shipyards can make them, and they're being put to work immediately. DryShips (Nasdaq: DRYS) is one company that made a big bet on deep water that is paying off. The company now has four ultra-deepwater ships in operation and another four under construction.

This month, Dryships signed a contract with Petroleo Brasileiro (NYSE: PBR) for the two ships that will be completed in 2011, for 1,095 days of work and a combined value of $1.1 billion. One of the company's older rigs, Leiv Eiriksson, also extended its contract with Borders & Southern. That leaves Eirik Raude as the only drill rig that doesn't have a contract through at least the middle of next year.

Seadrill (NYSE: SDRL) is also expanding its ultra-deepwater capabilities. It has the second-largest fleet of ultra-deepwater rigs behind only drilling giant Transocean (NYSE: RIG). Seadrill has 12 units already in operation, with contracts for two and options for two more.

As oil becomes more difficult to find in shallow water, the market for ultra-deepwater drilling units has exploded. According to Seadrill, 21 units were ordered between October of last year and February, when the company reported earnings. But those rigs won't be completed for a few years, leaving existing operators to reap the rewards now.

With an expanding presence in deep water, Seadrill in particular looks like a good bet for investors. Shares are trading at just 10 times forward earnings estimates and the company pays a 5.5% dividend. Dryships looks even cheaper at just four times next year's estimates, but the company hasn't been known as a great steward of shareholder capital, is still primarily a dry bulk shipper, and doesn't pay a dividend.

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