Honestly, Canary Islands.
In October, you ‘can’ get some nicer weather in the Med or other areas, but honestly if you just want the best chance of a nice beach/sea/swimming climate, then the Canary Islands are a much safer bet.
No doubt there will be some cretin along shortly telling us why they wouldn’t be seen dead in Tenerife and you should be in a vegan spoon whittling retreat on the far side of the moon, but this:
Feels more like a town than a resort (might not be achievable), i.e. isn’t full of cafes selling full English breakfasts
Is very easy to acheive with a bit of research in the Canaries.