Massively over-engineer the speakers, keep the water resistance, and enable music on WatchOS to allow for direct playback through the watch speaker itself. Yeah, maybe it’s a bit tacky, but could be useful for lots of situations when you can’t or don’t want to wear headphones. Plus, it’d be a funny way to flex on anyone with a S5 or older who can only play 30 second clips through Shazam.
The speakers on my S1 in my opinion are perfectly good enough to enable this through WatchOS, but we all know Apple would never do that... they’d want to brag about having the best speakers in a smartwatch or something before letting you blast music all about.