they say posidien is the only one who controls the ocean. but don't tell that to dan hayden who every day controls what some call the inside ocean here in the naval facility in bethoseda maryland. >> you spend your days creating waves in the largest pool owned by the u.s. government. >> this is a one of a type facility and allows us to produce any type of ocean. >> it is called mask. and it holds 12 million gallons of water. big enough to test models of every ship in the modern navy fleet. >> we test it and measure the motions and use that to predict how the ship will behavior. >> one of the problems is changing sea conditions. a ship that does well in the short chop of the north atlantic may not do so well in the rolling swells of the south pacific. mask has 216 individually controlled electromechanical wave boards and can recreate any type of wave from anywhere in the world. navy brass said it will keep our ships on the cuttingem for years to come. >> we can use them to sustain our modern float and project out in the future. >> reporter: t