The [censored] is with my pool? Elec engineers pls!

[Anacardo]

So I'm back in TX helping my mom move house. There's a pool in the back yard, ~20 years old, full-size, below ground. Some years ago I noticed that there was something leaking current into the water from the light on the deep end; if you get your head next to the light when it's on (since disconnected, obv), you see stars and taste metal. Just the other day I noticed the handrail is also running a mild current; if you get your hand wet, then grab it, your hand and forearm tingle with the slight shock. It's intermittent, though; sometimes there's no detectable charge. WTF could be causing this? Seems like something we might want to clear up before the sale.