I've been using the vestpac (vestpac.com) for hydration for skiing, biking, running and stand up paddling. The reason I love it is that it is a super lightweight, low profile pack that has a mesh design so it offers circulation. It has stretchy straps so you can really make it fit comfortably and it won't bounce or pull on the shoulders. But my favorite part of the vestpac is the handy chest pockets which perfectly fit my phone, ipod, snacks and sunblock. It also is great for running events because it adds extra support for "the girls"

I recently participated in a SUP race with my vestpac it was completely hands free so I could hydrate without having to stop paddling. I can't say enough about these!