I have another twist for a dry suit and those wearing it. Information
gleaned from am MED ( Marine Emergency Duties ) Course showed that if
you don't bleed off the air it can pool at the feet and legs if you
enter the water head first. ( Exiting an overturned kayak may be the
recipe for that ) you can be suspended upside down , feet in the air
head under water. Should this happen the answer is to go into a fetal
possition , hug your legs squeezing air out to other parts of the suit
and make a vicious breast stroke for the surface. It works.
Learning to swim is always an asset, I am a poor swimmer. I would never
disuade anyone from kayaking because they can't swim. Having a cool
head is important, knowing how to swim may help here but it is harfdly
nessesary.
Peter is of course right in that it can't hurt and will improve other
aspects of life.