Is it normal for a pinpointer to not pick up gold chains?

Actually, yes... If you are talking about a small thin gold chain necklace. Even high end full size units have a hard time with small, thin gold chains. You almost need to go with a dedicated gold detector for small gold like that. Something running high a frequency (40+ Khz) This is I think 2 or 3 Khz. Go for what it's meant to do, but it's not going to pick up small gold like a prospecting machine.

Is the battery replaceable

The battery in built in unit you will have to send in to be replaced

Can I drop in down into water on a pond and use it that way? How would it alert me?

I hope I understand your question correctly. You can set the PulseDive 2-in-1 to alert you by vibration or sound and vibration or sound. There is also a light on top that blinks.

Want to take out on boat for multiple dives. Need to know charge time, approx how long is it to fully charge?

I own this metal detector and it works EXCELLENT. The manual says it takes 4 hours to fully charge but my PulseDive only takes about 2 hours to fully charge. The manual says it will hold a charge for 6 hours, but my holds a charge for (very close) to 8 hours. I have the 5.5" black coil and the 8" yellow coil and everything works GREAT! I have used it in FL, Jamaica, etc and I have found so much (good) stuff.

Brand	NOKTA DETECTION TECHNOLOGIES
Batteries Required?	Yes
Power Source	Battery Powered
Item Weight	1 Kilograms
Adjustable Length	Yes
International Protection Rating	IP68
Global Trade Identification Number	08699394001131
Item model number	PulseDive
Product Dimensions	41.91 x 19.56 x 9.14 cm; 1 kg
ASIN	B07RL3GTVV

Nokta Pulse Dive 2-in-1 Set Waterproof up to 60m (200ft.) Pulse Induction Submersible Metal Detector Cum pin-Pointer

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