I see a lot of people complaining that the Fairphone 6 doesn’t have an Aux jack.
Just use an adapter cable.
A 3.5mm Aux jack takes up a significant amount of space just to connect a few wires that could be connected through USB-C anyway, that space could be used for a bigger battery.
Even if there was a good enough reason to keep Aux it should be 2.5mm Aux and not the usual 3.5 as it does exactly the same thing but uses less space
Perhaps, but there are many waterproof USB-C devices that you can swim with, so I don’t think it should be much of an issue.
Have you tried swimming while charging said device? Mobiles like my Pixel 7 will disable it’s USB port if it detects water. I doubt anything could have waterproof usb port outside of sealing the port with external mechanism.