This is my third Garmin watch (year 2018 - Garmin Swim, the best for swimmers, then in 2022 - Garmin Swim 2 - unusable as FR255, and now - FR255).
I see that the swimming activity algorithm was completely changed starting from model Swim 2 and (reading all other Garmin models forums) is still developed for all other watches. Unfortunatelly.
There is only one function swimmers need in a swimming pool - counting pool lengths (without pressing a button on every turn). Using that old "Garmin Swim" watch for a few years this function worked nearly perfectly and in my observation just light pushing the wall while turning with hand (no full flip was needed) was enough for the watch to "tick" the counter. More of ith - the watch was able to automatically "recalculate" (when clicking "Save") all the activity to correct potential wrong counting. But after the watch stopped working after a few years, I bought a new model "Garmin Swim 2" - it was a BIG step backward.
It is hard to find a description (in Garmin docs) of what is used as a counter trigger. Probably they look for a moment when you swim a few seconds after turning without moving your hands. It doesn't work. Especially, when I swim on my back with simultaneous (symmetrical) movement of both hands - I look at the watch and all the pool length the counter doesn't even start. You maybe can say that - ok, a few lenhgts in plus or in minus is not a big problem, but it is more of it. When you train a constant distance you can not make any comparison, any analyze and more of it - the watch saves you "virtual" records (sometimes I get better intermediate times than Michael Phelps ;-) ). Saying in one word - I was not paying for it.
The strange for me is that the watch can perfectly count my steps going up the stairs (the stairs are about only 20-30 cm high) but CAN NOT count about 30 full-hand moves through the 25-meter pool length. He just doesn't even notice it. Further - why it doesn't use the COMPASS to see that I turned and started a new length swimming in OPPOSITE DIRECTION?
As I said, losing lengths is not the only problem, sometimes it adds lengths and I can not find out what influences it. It seems like the watch makes a kind of calculation during activity and adds another falsification of results.
So, please Garmin developers - make the swimming activity usable, my suggestions are above. You can attract more customers or lose them. Now you are losing much...
p.s.
Settings colors on the watch face for swimming activity don't work - there is always a white background during activity and always a black background while resting (hard to read on the pool).