Most people's idea of what drowning looks like would be what they saw on tv or at the movies. A person shouting for help, hands over their heads trying to get someone's attention.
In actual fact, drowning is pretty much silent. The person would be too busy gasping for air to shout and too busy using their hands to keep their head above the water to flail them in the air.
Check out this news report from Fox 9 in the US.
INVESTIGATORS: Drowning is silent - KMSP-TV
Although kayakers have to wear PFDs while kayaking in Singapore, I have always believed that you should know how to swim if you're going to be involved in watersports.