Swimming for exercise

La
Is anyone swimming for exercise? I'm curious what is your typical exercise routine in the pool? I'm trying to get ideas of what I can do. I currently do spin 2 times a weeks and walk a lot, dr ok'd me to do spin just as I usually would but just making sure I listen to my body.
I love to swim but it's always been more for fun or because it's hot out. I want to start going to the local lap pool and swim some laps but I don't know what I'm really doing and I don't want to look stupid doggy paddling back and forth. 
Anyone got any good how to video links? Or recommendations or experience?
Thanks!