This power bank can be used underwater (but we don't recommend it) | ZDNET
Nitecore NPB2 waterproof Powerbank, 10,000mAh | Advantageously shopping at Knivesandtools.ie
Amazon.com: Nitecore NB10000 Gen II (Gen 2) Ultra-Slim Power Bank, 10000mAh QC Quick-Charge USB and USB-C Dual Outputs with Cables for Phones Flashlights and Headlamps (Black) : Cell Phones & Accessories