Get the Netgear powerline networking adapters. Use the 84 Mbps
versions. There is a set of two that they sell where one plugs in to
your router and the wall socket in your apt. The matching unit has
built in wifi and plugs in to any other wall socket on the
electrical. Should work all over you apts.
Take this second unit out to the pool and plug into a socket nearby
and make an AP at the pool.
Be sure to use security on the powerline system (read the
instructions) and also on your new plug in AP.