?This pack contain 14 different shape and size of placeable water plane, they don't have a fill trigger no, but yes you can dig under them.
square shape: 2m, 4m, 10m, 20m, 50m, 100m
?round shape: 2m, 4m, 10m, 50m, 100m
?rectangular shape: 2x10m, 4x20m, 10x50m
They are in the placeable, decoration "other" tab