Offshore drilling rig owners have had an awful year as low oil prices have caused oil explorers to slash capital spending. Long term, low oil prices will eat away at rig owners' revenue and earnings, something we're starting to see already.

But not every rig owner will be affected the same way. For example, Seadrill (NYSE: SDRL) has made over $1.1 billion in net income in the past year while Transocean (NYSE: RIG) and Noble (NYSE: NE) lost hundreds of millions and Hercules Offshore went bankrupt. How can companies in the same industry have such different fates? The answer comes down to what they're offering to the energy industry.

SDRL Net Income (TTM) data by YCharts.

Water depth matters
Drilling rigs are generally split into two categories: floaters and jackups. Floaters are rigs that float and operate in up to two miles of water, while jackups are literally jacked up from the ocean's floor, so they can only operate in a couple hundred feet of water at most. 

While not every drilling project has the same characteristics, generally we know that shallower water drilling contracts are shorter in length -- as little as a few months -- and ultra-deepwater contracts can be many years in length. 

This means that shallow water drillers are the first to feel the pain of low oil prices and the benefit of high oil prices. But it also means that they run much more unstable businesses. Seadrill, Transocean, and Noble, who all own large deepwater fleets, have backlog years into the future because of their floaters. Hercules Offshore, who focused entirely on shallow water, quickly succumbed to low oil prices because when short contracts ended there was no work for its fleet. 

There's no guarantee of success in shallow water or deep water, but the two segments come with very different characteristics and investors should know that when looking at offshore drilling stocks. For now, long contracts of floaters is becoming a savior of some of the industry's biggest players. 

Age matters
The other major component to look at is the age of a fleet. The younger a fleet, the better its capabilities should be and the more desirable to oil explorers. Adding to that is the lower risk a young fleet faces of being stacked or scrapped.

Image Source: Seadrill

You can see in the chart above that scrapping has accelerated rapidly over the past year and that's because old rigs aren't finding contracts and aren't valuable enough to maintain without work. So, owning companies with newer fleets is desirable to investors for their simple ability to stay in operation.

Now look at the next chart from October 2014, before scrapping really took hold, and notice that Seadrill has a much younger fleet than Transocean and Noble did. Both Transocean and Noble have scrapped and cold stacked a large number of units in their fleets, so it shouldn't be a surprise that they're reporting massive losses while Seadrill reports profits. 

Image Source: Seadrill

Age matters a lot in drilling fleets. When in doubt, you want to be with the companies who own younger fleets. They're more likely to find work for rigs and less likely to have to scrap them.

Not all drilling companies are created equal
It's easy to lump all offshore drilling companies into a single category, but the reality is that they're all very different. The rigs they own make their strategic positions very different and that has a direct impact on finances. Fleet age and water depth are the first things to analyze when looking at offshore drilling stocks. 

Rather than selling off all offshore drilling companies like they're going to sink along with oil prices, maybe it's time to opportunistically buy the companies that are best positioned for a recovery. I don't think oil will stay under $50 per barrel forever and offshore reserves play a large role in the industry's long-term ability to supply the world with oil. 

If prices do recover, Seadrill looks like one of the best bets for when oil prices do spike and it has a nice backlog to weather the storm in the meantime.

Travis Hoium owns shares of Seadrill. The Motley Fool recommends Seadrill. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.