Excellent question! The debate goes on: snorkel or no snorkel. A couple items I consider: 1. At the surface, at 1 atmosphere, we use very little air from our tanks, and your regulator is the safest way to swim. 2. When fighting waves while swimming with a snorkel, residual CO2 in the snorkel will frustrate our swimming over time. 3. In full scuba gear my preference is to inflate my BCD and float/swim on my back.
One of the issues with carrying a snorkel is that modern snorkels are very large and bulky. A happy medium may be to not carry your regular snorkel but to invest in a hybrid collapsible snorkel. Divers I’ve spoken with tell me the good one maintain their rigidity even in strong winds and waves. Stow it in a BCD pocket or clip it to a D-ring; you won’t know it’s there unless you need it.
Here's an example from Aqua Lung:
https://www.amazon.com/Aqua-Lung-Sport-Nautilus-Snorkel/dp/B00ITCB34I/ref=sr_1_6?ie=UTF8&qid=1495718113&sr=8-6-spons&keywords=collapsible+snorkel&psc=1
