If your diving is "strenuous" something is going wrong or you're a commercial diver. My diving is leisurely, relaxing and fun. Last emergency I had to help with, we were back on the boat shortly after...plenty of water there.
Ahhhhh.....I'm just a minimalist when it comes to what I take into the water. Enjoy your water. I'd recommend a splash of raspberry or squeeze of lemon.
Change "strenuous" to "physical" then if it helps you to understand. The semantics may change but the point is the same.
If you're a minimalist I assume you just carry a tank with a regulator. No need for frivolous stuff that can get you all tangled up like a mask, fins, BC, etc, right?