Okay, I'm going to weigh in here. The snorkel allows the diver to surface and keep his/her eyes underwater. In the 1960s I was doing freediving in cold water with limited visibility as a spearfisherman. We dove off paddle boards at times. The snorkel was used to keep eyes down, and if we dove deep we spit it out while surfacing if we really needed a breath. If not, we simply started exhaling as we surfaced while looking upwards, which displaced the water in the snorkel and it was clear when we got to the surface. It's called the displacement method of clearing the snorkel, rather than the "blast" method. Both work, but I like the displacement method better. Freedivers have used snorkels without problems since the early times of diving.
I have never had the snorkel cause my mask to flood. If that happens, I think there is something wrong with the snorkel.
You will want to use a low volume mask with nose pockets so that equalizing is easy. The low volume means you don't have to add much air to the mask as the pressure increases with depth.
We would buddy up, but the buddy would watch from the surface and be available if something happened.
As to instruction, you need an instructor familiar with shallow water blackout (SWB), its prevention and its causes. SWB can be prevented by not hyperventilating and taking no more than about two or three deeper breaths before diving. I do not advocate the freedive instructors who advocate for training to do deep dives, packing breaths, etc. It is much better to become a scuba diver, and breath underwater, than to try to break records (personal or other) or extend breath holding times using various techniques (see my explanation for rhythm diving below).
I have long advocated using a "rhythm diving" method too, where you dive underwater without hyperventilating until first feeling the "must breath" signal, then surface. Breath normally for about two minutes, then dive again. Over time (15-20 minutes) you'll be extending your time underwater by relaxation and your body's adaptation to the breath-holding.
SeaRat