At least if my mud hut in Topsham floats away (about 5m above high tide, though with extensive flood plains, an estuary, and the sea - at sea level - just five miles away), I've got one at 500m ASL to escape to, in extremis.
I'd be less sanguine in one of the Topsham houses whose ground-floor rooms are often below the level of the higher high tides. Their insurance premiums must be 'interesting'.