Speaking from my own personal experiences, *full grown* bantams and Silkies can and do drown in even the shallowest of kiddie pools.
OP has 6 bantam pullets and 5 silkies. Some of my bantam pullets are only 5-6" tall.
OP has 6 bantam pullets and 5 silkies. Some of my bantam pullets are only 5-6" tall.