Performance depends heavily on the underlying technology rather than just the price.

Lightweight PI performance designed for extreme mineralization. Nokta Gold Kruzer 61 kHz high-frequency and fully waterproof up to 16 feet. Choosing the Right Technology

Ensure the unit has at least a waterproof search coil for hunting in creeks. If you plan to submerge the whole unit, verify it has an IP68 rating. Where to Buy Safely