First season at it

Hi all!
My name's Joe, I'm 28 years old and live in Queenstown, New Zealand.
I'm new to triathlon, and am in the very privileged position of having a partner who is a very impressive age group racer, with big aspirations, and I have her to thank for getting me into this!

I've really enjoyed training - some on my own, and most with my partner - and can't wait to get into my first race. Like many newbies, I'm very anxious about the swim. I have always been able to swim, but have never been great at it, and certainly not over any sort of distance. i've had a couple of lessons with an instructor recently, which was a good help, but i'm still only at the stage where I'm trying to get comfortable in the pool without getting out of breath after 50m (so frustrating when I'm otherwise pretty fit!)

I feel strong on the bike, and have done a lot of running, and have done a few brick training sessions, so i'm not too worried about those. But i have the opportunity to enter a sprint race this weekend 11/1/20 and I'm very apprehensive.
I've never swam in open water (though planning to fix that this week) and I've never been able to relax in the pool and cover more than 50m confidently.

Any recommendations? I'll continue to do loads of work on my swim, but I'm tempted to just throw myself into it and see what happens. I'm confident I won't drown, but I may be last out of the water by a long way - good motivation to put a strong bike-run together i guess!

Anyway, good to be here! Thanks for having me. You guys seem awesome.
Cheers,
Joe