[johbjo]

It seems the easiest and coolest way to make a watertight case would be to plug the usb-port with hot-glue and then pot the assembled board in resin (epoxy/polyurethane). Either pigmented or clear.

[numpad0]

There are special "cap-less"/cap-free watertight USB receptacles for phones

Ref: https://www.jae.com/en/releases/detail/id=1739

[taf2]

Might try nail polish as suggested here https://youtu.be/h8ycmroFQSs

Just brush it on. Should keep the electronics safe from moisture and maybe survive a quick dunk or two

[RantyDave]

Unfortunately antennas don't like being embedded in epoxy. See https://www.pet1.net/post/new-case-design

[criddell]

I think the USB port is required to charge it.

[taylorfinley]

That's why you'd plug it with hot glue, it could be easily removed after the resin cures. Better yet use black silicone and make it reusable.

[seltzered_]

inspiration - the CW&T solid state watch: https://cwandt.com/products/solid-state-watch?variant=346829...