This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 湽 is uncertain. It visually contains 氵 (water) and 田 (field), but the origin and original meaning are unclear.
With water 氵 beside a field 田, you might imagine irrigating a field, but the actual meaning is unknown, so this is just a visual reminder.
For シ, picture a sheet of water (シ) flowing over the field: sheet -> シ, though the kanji's meaning is uncertain.