KPV

Did you take all that photos with similar settings? What was the white balance?

I ordered stix floats, but they delivery seriously delayed. I need to find some solution for an upcoming trip. I definitely give that material a try. I found that material may have compressive strength from 0.15 to 0.5 MPa (1.5-5 bar), but I don't know what kind of material I have. So wish me luck.

Can expanded polystyrene withstand 30 meter depth?

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2200 mAh sounds totally legit. I guess 3600 model number it's rounded mWh.

I don't believe it. We need some tests to confirm it's capacity. For what I know best 14500 (AA) Li-Ion batteries have around 1000 mAh. At 3.7V it's 3.7 Wh but the ad stated it's 4.89 Wh. The battery inside should be shorter than 50 mm to leave a space for a voltage stabilizer and charging circuit. So in my guess 1320 mAh for the lithuim inside is a scam. I've found 14430 with 1050mAh capacity and it's 3.78 Wh https://keeppower.com/product/keeppower-14430-1050mah-protected-li-ion-rechargeable-battery-p1443c3/ And another 14430 with 1300 mAh and it's 4.81 Wh https://www.akkuteile.de/en/lithium-ionen-battery/size-14430_100212_3661 So it looks possible if not take to account losses on DC-DC transformation. But it has low constant discharge current, so I think it would have low max pulse current.

White fins and buddy's aluminum cylinder which is gray. In video mode white balance must be set before shooting. If you really want to get technically accurate colors you can use cheap and large color checker analogues. But I think it would be inconvinient to carry and use during a group dive.