The Golden Pool is a small pool with no inlet or outlet. Water wells up from below and is carried off by an underground stream. The trees and grass around the pool have a golden sheen and goldfish (or koi if you are feeling more obscure) live in the water. No animals go there, although birds and insects abound.
The native tribesmen avoid the Pool. In their legends, the Sun came down to drink there, and the place is both holy and taboo.
The water turns everything into solid gold. Splashing, or a few drops won't do it, the item must be immersed to be turned to gold.
Getting the statues out without being statufied yourself might be a problem. A grappling hook on a rope wouldn't work, since the rope would be turned to gold and would probably break. A pole with a hook on the end might work, although hooking a statue and getting it out would be difficult, and the likelihood of an accidental immersion of a hand or foot would be rather high.
The water looses its virtue after being carried away from the pool. A bucket of the water would have the ability to turn one or two things to gold before becoming ordinary water. Thus, no instant bankers.
The carp? Are they living gold, or are they immune to the effects? Catch one and find out!
1) Legends abound of a place where golden statues litter the bottom of a pool. Instant wealth for greedy PCs.
2) An alchemist wants a sample of the water to analyze and or to make some item, and hires the PCs.
3) The son of a nobleman went looking for the Golden Pool and didn't return. The PCs have been hired to find him, or return with proof of his demise, such as his signet ring, before the will is read.
(With inspiration from The Voyage of the Dawntreader, by C. S. Lewis, one of my early favorites)