Be careful when looking for the Energizer, they make several models sold in the same package. Look for the one that has the 250 Lumens on the package or you might end up with only a 80, 150, or 200 lumen lamp and not the 250. I have to go check this one out it just might replace my ROAM (keep reading)...NOW...BUT let me finish here.
In my 30+ years water detecting I have used several "flashlights". Incandescent and halogen no longer have a place in my house - gone to LED lighting. Today I have three LED lights that I would not do without (unless I need to replace one).
Two are Princeton lights, both are waterproof. The Impact II is a handheld flashlight 65 lumens and 50 hour run time, twist on / off and I hang it around my neck on a piece of nylon cord. The second is the Princeton Roam a "headlamp" 100 lumens and 18 hours run time, twist on / off, worn on the head with straps.
My third is a "KILLER" no brand name, but search for 15000 lumen 9x CREE XM-L2 LEDs on the internet and you will find it. The lamp alone is reasonably price, but the rechargeable battery is a bit pricey. I have two battery packs as on HI a charged pack only last about 2 hours. The lamp does have HI-MED-LO brightness settings and a strobe setting. It is NOT waterproof, so I keep the battery pack inside my waders and do not dunk my head in the water. A splash will not harm the unit, it is just not submersible like my other two go to lights. BUT this light will light up the neighborhood, scare snakes and boars away and will attract fish. At least it allows the fish to be seen at night. The target digging and disturbing the sea bed actually attracts the fish as they look for food. Word of caution with this lamp, it is heavy for wearing on you head, although I have and use the head mount for it. The battery pack (6x18650 Li-Ion cells) is wired and hangs off your belt or inside waders. way too heavy for head mounting. Whereas the ROAM has 2AA cells in the lamp casing.
OK, now you know my weapons. Here is what I look for:
MUST have HIGH intensity LED(s) - 1052 lm are great CREE XM-L2
Lumens is the light output measurement that you should compare. I have a 65 - good for in the water, 100 - better for water and land. Newer head units are above the 200 mark and that is were my next headlamp mount will be spec'd at.
LEDs like at least 2.85 to be useful. This is where more cells in the battery pack give longer run times (more voltage and current).
A 6 volt power system (4AA batteries). The Impact II has 6v, the ROAM only 3v (2AA) and the KILLER 8v rechargeable Li-Ion (6x 18650) pack. A 6x 20650 pack would be much better for twice the run time, only price holding me back right now - that is why I have 2 packs. And the Energizer 250 is powered by 3AA cells (4.5v)
Weight: not much concern if worn around your neck, but on the head, the lighter the better...but you will give up run time with lighter weight units (including battery (pack or cells).