I do like the beach idea as I don’t like being upside down in the water.
But as a floatplane pilot, I have taken what is known as the ‘Dunk Course’. Something that is now mandatory in Canada for commercial floatplane pilots. It has a setup in a pool designed to simulate an aircraft cockpit which flips you upside down and then you do your escape procedure.
One thing about flipping over on a beach rather than water that I wonder about is the possibility of the harder impact on the beach making fuselage deformation more likely with a more likely chance of a jammed door. Definitely a good idea to open the doors for the touchdown.
Another advantage of being upside down in a water-filled cabin is that undoing your seatbelt may mean that you won’t be as likely to fall onto your head when the seatbelt is released.
One note on seatbelts in upside down aircraft. If by chance the buckle has somehow been done up with it facing the wrong way(release toward the body) as can happen with a passenger who is not familiar with its operation, it can be impossible to release when one’s body weight is against it while upside down. This situation did occur and can make a timely rescue extremely difficult in a situation where full or partial submerging in water increases risk.