Both the Beats Studio Pro and the Solo 4 headphones let you use their USB-C port for more than just charging. They can deliver lossless, hi-res audio straight from a Mac or a USB-C-equipped iPhone.
If you need a speaker for pool parties (emphasis on the party), get yourself a Wonderboom 4 or two. We say two because they're only $100 each, and they allow you to sync two at a time to one device.