There are several ways to control your x10 via Alexa.
The the Broadlink RM pro will work with X10 if your x10 receiver is working but not the transmitter.
Also you could look at itead Wi-Fi modules which are very cheep one could be wired into your lights power run.
There is an Alexa skill for them as well.
I run both with Alexa however I don't have a pool.