ideally you would move your wifi router to a window facing the pool.
the setup you are describing would be VERY lucky to get a regular home router to work consistently.
wifi range is affected by many things, like walls, atmospheric interference, RF interference from other devices and more.
that's why your retail router packaging doesn't usually post a distance range - because it varies depending on environment.
some routers are better than others at transmitting, even if they both use wirelessN.
(what you want to check is the power supply - crappy routers use a .5 amp power supply, good routers use a 2 amp power supply)
what you need is an ubiquity nanostation m2.
http://www.ubnt.com/nanostationm
nanostation loco i guess is the newest one.
it takes a little tech saavy to set it up, but it has an awesome range.
i have a setup at one customer using two of those and it connects two offices nearly two blocks away.
just installed one at another customer who now has reliable wifi in his shop nearly 200ft from the house.