Being a little anxious before doing anything new is normal. Being terrified is a warning sign. Scuba is not for everyone.
Ask yourself why you are getting certified? If it is not
because YOU want to...don't. Do not get certified to please anyone but you as that will not make you happy and just puts you and everyone around you at risk. Life is short, do what makes you happy, not what causes issues in your life.
... I'm absolutely terrified. Part of the fear is that, during training, it took me forever to learn to clear my mask....
It often takes a bit for people to get the hang of this. I hate water around my nose, or I should say I use to when I first got certified. Now I am comfortable with it. Practice in tub or better Jacuzzi. To do it right you need to be able to keep your head in the water, look up so the water inside the mask is next to your skin, press gently on top of mask and exhale through the nose gently.
... What happens if my mask falls off under water?...
Usually it sinks. This is a rare occurrence. I teach and dive with divers who are disabled. Paraplegic and double above the knee amputees swim with their arms, which means I have a greater risk of getting my mask knocked off. So far it has never happened. A mask strap could break, but you check your gear for wear and tear before and after a dive so that should not happen. A seal or sea lion could pull it off if they grab your snorkel to play keep away. So what happens? You calmly reach into your pocket (pockets on dry or wetsuits are great) and retrieve the spare mask you carry and put it on.
... I have an anxiety disorder and panic easily. ...
Um... Not a good thing in SCUBA Divers. Panic can kill if you bolt for the surface and injure other divers who race after you to keep you from injuring yourself.
...I would be much more relaxed if our first certification dives are in a bay or lake. Do you think that the instructor would allow that?
Your instructor could. But answer this question, The open ocean and the bay or lake are all environments that have the following in common 1.) Water 2.) water that is going to exceed 20 feet, 3.) animals such as fish etc and 4.) you on scuba at 20-60 feet. So what is the difference between you diving in a bay or lake rather than the open ocean? How would that make you less anxious? What are you anxious about exactly? I find it humorous that people are fine SCUBA diving in water 100 feet deep, but panic when you suggest a dive to 40 feet in water 1,000 feet deep. Anything over 1/2 inch is enough to drown in. So what is the difference?
... Sorry if this post is a little messy, but im having anxiety now just typing this.
This is a real red flag. If just thinking about it has your heart racing, this may not be the sport for you.
Before you go any further spend some quality time alone and think on these things:
1. Why do
YOU want to SCUBA Dive? If it is not you who wants to dive, then don't.
2. What exactly is it about SCUBA Diving that makes you anxious?
a.) The water?
b.) Being Under water?
c.) Being 30-60 feet down?
d.) The marine life? aka sharks. (Shark week causes a lot of fear with their unnatural portrayals of sharks. They chum the water with blood and meat/fish for days to attract sharks that are excited and not acting as they normally do. There are youtube videos of a lady snorkeling and holding the fin of a Great White and taking a ride repeatedly. They are not the monsters shark week makes them out to be. If you want to fear something, be afraid of the vending machine as that is significantly more likely to kill you than a shark.
e.) Fear of drowning? Then don't drown, check your air and keep the regulator in your mouth and breathe.
f.) You don't have a specific fear, just general terror. If this is it, I would suggest you would be much happier with another sport.
Identify you specific fear/panic/terror and then decide if this is something you want to challenge and conquer or not. IF this is a significant fear, you need to conquer it BEFORE you go SCUBA diving. Underwater on compressed air is not the place to work on issue you should solve in therapy or in a bath tub first. Again, do what makes you happy.
Life is short, do what makes
you happy. If SCUBA upsets you, then do what makes you happy. Don't do it to please a friend.