Things have been coasting along nicely for Steiner Leisure (NASDAQ:STNR) lately. Since being recommended in the Rule Breakers newsletter service four months ago, the stock has risen by 45% as the floating spa specialist continues to make all the right moves. Its latest catch? A lengthy contract renewal with Royal Caribbean (NYSE:RCL) and Celebrity Cruises that was announced last night.

Steiner is at the mercy of the cruise lines to continue welcoming the company onboard to run its spas, so these renewals are a big deal. Yet it may be fair to say that the cruise lines are now at Steiner's mercy to keep the lucrative landlord-tenant relationship going.

Consider: Last month, when Carnival's (NYSE:CCL) Princess Cruise Line renewed its contract with Steiner, it even returned a pair of ships to Steiner's skilled hands. Princess' in-house spa manager had resigned when the operations just weren't living up to Steiner's production on the rest of the fleet. That was a huge win for Steiner. It's the head on the spike that will warn others not to stray from Steiner's decades of floating spa excellence.

But Royal Caribbean and Celebrity didn't need any kind of threatening affirmation. Royal Caribbean has been a satisfied landlord for Steiner since the 1980s. Yet if Carnival had made its internal spa work, it could have swayed others to test the waters.

Locking up Royal Caribbean and Celebrity for the next four to five years means more than just securing 28 of the 114 ships that Steiner currently services for both cruise lines. Royal Caribbean will also be handing Steiner its new breed of "Freedom" class ships as they leave the shipyard.

Steiner does more than just run spas for large cruise ships. It also runs resort spas at some of the ritziest hotel properties, such as Starwood (NYSE:HOT), Hilton (NYSE:HLT), and Marriott (NYSE:MAR).

The company has beaten analyst estimates for 10 straight quarters. It goes for 11 later this month. Reinventing the way that spas pamper cruise passengers has made the company a winning Rule Breakers selection so far. After its key renewals in recent months, the company looks to be in calm and inviting waters.

Need some more reading while you lie out on the massage table?

Longtime Fool contributor Rick Munarriz has been a Steiner customer on the Disney Wonder, and while he does own shares in Disney, he does not own shares in any of the other companies mentioned in this story. (The Fool has a disclosure policy.) He is also part of theRule Breakersnewsletter research team, seeking out tomorrow's ultimate growth stocks a day early.