I feel for you, swimming is one of the tougher mid-transition activities to approach, and has been a source of anxiety for me as someone who prefers to spend the majority of their waking time in the water. I'm writing this around the take of someone who is still presenting in their natal sex for whatever reason. Not sure that is entirely your case, but it has been mine and will probably continue to be for the foreseeable future.
I had to deal with it quite a bit this summer with friends and family I am not out to, and I'm nowhere close to passable after two years of HRT, coupled with being a sensitive conformist, so pretty much mentally stuck presenting male. What worked for me...
Best: A male wetsuit long sleeved top by itself gave enough compression (I'm not huge, but I can't wear a t-shirt alone without being noticed. In the winter, just straight up full suits.
Secondary option: competitive women's swimsuit underneath a rash guard (they give compression). Worked fine, front is well handled, but you can probably see lines through a solid pattern rashguard that is wet. A rash guard only can work, but depending on your projection, you may need to be strategic with your arm placement when out of the water. In the water, no one sees a thing.
Indoor pool is a bit trickier, since nobody expects you to be wearing a wetsuit in the pool and you don't have an excuse to protect yourself from UV.

I was thinking about wearing a triathlon swimskin. Drawback is they are pricey.
On the pickleball front, if you're still presenting male at the time, men's compression tanks or sports bra under a shirt are the way to go. The latter may expose itself under heavy sweating though, not that big of a deal in my book though.
My therapist said there are some swim binder options out there too, but I haven't looked into them much. Pretty happy with the outdoor solutions above, indoor pools aren't that necessary in San Diego.