It's definitely important to teach kids to swim, but forcing a screaming, very frightened child into the water (eg. by just throwing them in) sounds counter productive and possibly traumatic. It makes more sense to take it slowly and let them get used to the water first.
Yes they should be encouraged, and gently. Swim instructors are fantastic. It would have been nice to have learned how to swim earlier rather than later, to not face the embarrassment of learning to swim in the babies pool in the final year of primary school at age 11!
Yes I believe a child should be taught how to swim, especially if they are afraid of water. Swimming instructors are skilled at teaching children how to overcome their fear in a safe caring environment.
Unfortunately there are swimming instructors and swimming instructors. I would preview methods before committing my child to any particular swim school. I put my son into a swimming class as an 8 month old. He was terrified. All he got out of it was a case of the giiardia parasite. Subsequently I strapped a bubble on him (Shock! Horror!) and he eventually let go of that at age 5. He went on to become a school swimming champ.
Good question! My son didn't want to learn how to swim and we certainly didn't force him, but took him to the pool as a family outing a few times until he felt more comfortable around water before getting him professional swimming lessons. He loves it now because he wasn't forced. I think it's up to parents to set a good example for our children and show them how things like swimming can be fun.