I am going to have a custom PWC trailer built and have been going back and for about brakes. Considering either electric drums or Disc Electric-Hydraulic. Any opinions? Looking for low maintenance and best operating system.

That must be one heck of a PWC trailer to even need brakes. I have Kodiak discs on my boat trailer, and they work way better than any of my utility trailers that have drums. Changing pads is obviously way easier. What size wheels and axle will your trailer have?

What is required by law and what is safe especially for long trips is different. My current trailer has no brakes and very light duty...hate pulling farther than local marina. Wheels will be either 14 or 15 most likely.

I like the disc, they dry out easier after you dunk them. The drums dont seem to stop too well after you load to go home. Also, the drums can hold sediment that causes issues after time.

i would agree electric brakes for a jet ski trailer, unless your talking four of them. I would do electric over hydraulic for marine applications, but if your talking 2 skis or less would seriously rethink the need for them all together

How can electric drums work if they are in water? Wouldnt they short out?

Nope. They work fine under water They are just sealed electromagnets. There are no electric moving parts at all. I've used them for a long time and they work great.