Usually people consider those "solar" lights like a flashlight (no restrictions at all). I am not sure if that is an accurate assumption. IMHO 12v is 12v. There may be a little difference between AC and DC but the battery in a solar light still has plenty of current available. If "DC" makes it safe, put a rectifier in the Malibu transformer.
BUT ... I don't think that changes anything.
"Tingle" voltage gradients in a pool are usually just a couple volts.
