I teach in the north atlantic ocean all year round.
At no stage would I enter the water with just a life jacket. you will need a wet suit or immersion suit. and a locator beacon.
I cannot see a foam box withstanding the waves either, so an inflatable airbag would stow easier and provide more benefit to you in the water.
When you're here in Ireland I can show you 'True Cold' with a hot whiskey afterwards.
Lake Como does sound very appealing on a Monday !
Enjoy your trip,let us know if you need any more info about the Green isle.
Fionn