Up here in sunny Glasgow we called them sannies.
When I was at school in the 70s/80s (round Bannockburn way) actual sandshoes were sannies, and gutties was what we called shoes for PE/gym class generally... So all sannies were gutties, but not all gutties were sannies...
Or more accurately we called them gu''ies, with a double glottal stop, cos... y'know... Scotland.