Not overly relevant to the OPI was lucky in having a council run swimming baths 5 minutes walk away when i was a youngster. My uncle taught me to swim and we also went there from junior school. So i got used to the water at an early age.
Not overly relevant to the OP
Go get lessons, most public pools offer adult classes
Well yes, but that ship has sailed for the OP and he's looking for help as an adult wanting to learning to swim
I had lessons as a kid too, but I'm not a good swimmer nor do I much enjoy it other than on holiday to cool down. I'm not nervous in a pool but I am in the sea, but that's probably because I'm just nervous about situations out of my control like currents