As often as I can, especially when the moon is full and there is a minus tide.
Protected lagoons are best as you do not have to worry about waves and sharks like to be able to get to deeper water fast.
I would not carry the scoop on my shoulder, as it makes it more difficult to hold your balance.
Instead, I use it as a staff, slightly in back of me for balance and move it forward to push me back to shore if I get in to deep.
Using a light, scuffing your search coil on the bottom, and digging tend to attract bait fish which often follow. At times fish after the bait fish, or the bait fish will attack the flash from the shiny basket. I definitely, would spray paint the basket of my scoop with a dull neutral color primer, such as black, if you hunt in an area where there are great barracudas, which would be a greater fear to me than sharks.
Further, wear protective gear, again black is best - especially if your skin is white, to avoid tempting a shark, and protect your self against stings by man of war/ box jelly fish and shower as soon as you can after you get out to avoid the itchies.
Large sharks often come in shallow at night to feed and leave when it gets light.
If you think, that you are safer in knee deep water, think again.
I have seen them in surprisingly shallow water (ankle deep) feeding.
I have yet to see a large shark, since I moved to Hawaii, while shallow water hunting.
I don't expect to see any close, as I suspect that the electro magnetic field from the search coil, would confuse the sense that a shark would use such as a hammer head to zero in on a buried flounder in the sand. The great white shark also relies on an electro magnetic field when attacking, as it cannot see at the time because of a protective membrane across its eyes to protect it.
I fear my fellow man far more than critters with teeth in the ocean.
Fear is good, as long as you are able to control it since it adds to the excitement.
If you have to justify finding gold being worth the risk, you should not be out there at night.
Low tides lately are hitting right at sunset... I'm a water person but a little nervous about wading in waist deep water at night with a shiny metal scoop. To me it seems like a bad idea.
Do any of you hunt waist deep in the dark?