• 潟かた — lagoon / inlet
• 干潟ひがた — tidal flat
• 潟湖せきこ — lagoon (formal)
• 砂潟さかた — sandbar lagoon
• 新潟にいがた — Niigata (place name)

潟 uses the water radical 氵 to indicate something related to seas or rivers. The rest of the kanji provides the sound and meaning of a geographical feature shaped by water and tides. You’ll often see this kanji in place names, such as 新潟 (Niigata), where shallow or receding water creates unique landforms.

干潟ひがたには 多おおくの生物せいぶつが生息せいそくしています。
Many organisms live in tidal flats.

新潟にいがたは 米こめで有名ゆうめいな地域ちいきです。
Niigata is a region famous for rice.

海うみと潟かたの境目さかいめが見みえます。
You can see the border between the sea and the lagoon.