noun, noun or participle which takes 'suru'
tide watching; watching the tide
Especially associated with the Naruto Strait whirlpools. Can be used as a noun or with する to mean the activity of observing the tide.
See also: 鳴門 (なると)
鳴門海峡で観潮を楽しんだ。
I enjoyed tide watching at the Naruto Strait.
観潮船
I went to see the whirlpools on a tide-watching boat.