thats nonsense. if you take it that way then every time i go swimming im being Baptised, as i'm immersed in water.
You are, in terms of the Greek language, especially if someone dunks you.
But think about your metaphor...
In my case, I became a believer early in June 1979. I was not baptized until two weeks later. Between the time I came to faith and my baptism in church, I went swimming with friends. While we were messing around in the pool we dunking each other, went diving, and generally did what teenagers do.
Was I baptized in the swimming pool at the local park, or was I baptized on the Sunday evening two weeks later?
It's not just immersion, but a public profession of faith.