rising tide; incoming tide
Refers to the tide when it is coming in or rising. Often used in contrast to 引き潮 (ebbing tide).
I checked the time of the rising tide before going fishing.
When the incoming tide rises, the beach gets narrower.
Compound of 差し (sashi, 'approaching, coming in') + 潮 (shio, 'tide'). The exact historical derivation is straightforward.