If you wear an automatic inflatable life jacket, when you fall into the water, the inflator mechanism will start automatically. The inflation will be completed within 3 seconds, no need to manually pull the inflator. So, automatic inflatable lifejacket is more suitable for non-swimmers.

A manual inflatable life jacket needs to be manually pulled the inflatable device to inflate the jacket, when you fall into the water, swimming or in an emergency. So, it is more suitable for swimmers.

Always make sure you know what type you’re wearing and if it is suitable for your activity.
All inflatable lifejackets will come with a manual override, make sure you know where it is.