Only extremely few foils will float - I dont know any actually....
If they are really thin (low drag) and strong like carbon foils, they dont float.
Aluminium foils dont.
It does not matter unless you got a very bad connection where it could be lost.
In terms of how fast it "sinks" when waterstarting especially strapless - it does not really matter.
Of course really heavy alu foils/masts sinks back to vertical a lot faster, but it is only a matter of "getting used to", and you will be fine IMO
Having said that, I still love lighter carbon foils myself, but simply a luxury thing, nothing but that