They had no freezer to use and had to use other methods to change the water after having agitated it, freezing is easiest.
(They; had; no freezer to use) (freezing; is; easiest) (They; to use; other methods; to change the water after having agitated it)
They freezing They
had is to use
no freezer to use
easiest
other methods to change the water after having agitated it