no, but what bothered me was the pressure on my chest and not being able to breath through my nose

No, but then I've never tried to scuba. Was the water cold? Was it the first time that you'd been in the water fully-equipped?

Not myself, I was a water rat since I was old enough to walk. Those that are comfortable in the water rarely have an issue. Those that have a little insecurity about being there will usually have that insecurity start a snowball possibly leading to panic. Humans weren't designed to dive. It's natural that you have a little fear. It's also natural that you breathe through your nose but that mask won't let you do that. That adds a little more to any insecurity you have. You're doing something not natural to you. I tried to get my exwife into the sport with a resort experience in a pool. Ever seen a Polaris missle launch from a subamrine? I did. The second she knelt in the shallow end and got her eyeballs under she managed to fly out of the pool landing with a helluva thud on the deck in a full blown panic. Impressive what with about 80 pounds of gear on. She was fine until her eyeballs were looking up and not down to the water surface and realized where she actually was. She's a good swimmer. It was all in her head and she couldn't deal with it.

I haven't personally but I've seen many people react that way. The idea of being underwater is very scary to a lot of people and it's very easy to start freaking out if you get water in your mouth. With water getting in your mouth, it's easy to start panicking and thinking about drowning.

It's a normal reaction like walking on a mountain. You have to gradually desensitize yourself. If you had no fear of drowning that would be abnormal.

After reading the comments here, I see that your first dive was in open water, is that right? That's very strange. Is this a class for certification? Under what organization is this certification? Classes are usually given at poolside after a little classroom time. You should be comfortable with a snorkle first. The snorkle teaches you how to clear out water by simply blasting. You have to learn to always leave a little reserve of air in your lungs. You snorkle until this becomes second nature. Then when you're on a regulator, it's the same thing - just blow the water through the regulator to clear it, then suck in some air. It's a great device, but you should be given time to get to know it in the shallow end. It's not unusual to see these little moments of panic in students. That's why the initial classes are held in a controlled environment such as a pool, and students are encouraged to snorkle whenever possible before certification. Never forget, no matter how confident you become, that you are on a life support system in an environment that you were never meant to spend more than a few seconds in and never deeper than a few meters. Remember that, and spend the time required to get the feel of the equipment, and you will be OK. This is truly second nature stuff, it has to be learned. Just being weightless in an alien environment is well worth it, though.