A lot of people do that sinus washing where they carefully pour water up their nose to slosh around in the nasal sinuses and are drained. I believe there were a few cases in u.s. when the water used was contaminated with the amoeba.
I would rather drink lots of water(if it would be ok, considering any condition I have) to dilute sinus secretions, rather than risk putting some bad stuff up my nose.
It is a wonder is is not more common from swimming. I have heard of a few cases where it came from a water heater that was not at a high enough temp to kill them, it breeds them instead.
Use distilled or boiled water in nasal irrigation devices