Been there, done that. Until I did my first race, I was petrified. In 4-ft water. Surrounded by people. After swimming almost a mile through freezing, kelp-infested water like a boss (I can say in hindsight), I realized I could take on anything. But I had to do that first. Now I surf and swim and stuff.
Adding to Susan's race advice...even though it's indoors, if you get a chance to be in the water before the race, try to put your face in the water and hold it there for a bit. Somewhere safe, where you can touch the bottom, or hold onto the side. That's a big thing for outside races, especially in cold water, but I'm willing to bet the psych effect will help you a little in the pool as well.
Good luck, you can do it!
2001 Cannondale R500 <3
2011 Specialized Ruby Elite Apex
2021 Tangential Speedarama