IO540 raises an interesting issue around risk management.
It may well be that for a short cross channel transit - using the minimum overwater route on a clear calm hot summer’s day to show off your Cirrus - a raft on its own is a reasonable option. Lots of people around in the air and the water to provide assistance and the route is well within the SAR coverage. However, if you plan to go to Ostend direct routing out over the CLN VOR in an old hired club hack - an aircraft that you got a cheap deal on so the owner could get some money out of the remaining time on the engine before it goes for an overhaul to zero time - then a life jacket, dry suit, PLB, and a life raft may well be needed along with a lot of good luck.
It’s a question of the correct tool for the job. This was what interested the GASCo people at the seminar about the Canadian risk management approach. It was suggested that with this approach there is no one size fits all; that, it was necessary look at what the mission is, work out the risks and then take what you need to manage them down to a reasonable level for your flight.