• 貝かい — shell, shellfish
• 貝類かいるい — shellfish category
• 貝細工かいざいく — shell craft
• 巻まき貝がい — spiral shell
• 赤貝あかがい — ark shell (edible)
• 巻貝まきがい — spiral shell
• 貝殻かいがら — seashell

“貝” was originally a pictograph of a cowrie shell — a traditional currency in many ancient cultures. This connection to value can be seen in other characters like 買 (buy), 費 (expense), and 賞 (prize), all of which include the 貝 radical.

海うみで 貝かいを 見みつけました。
I found a shell at the beach.

子供達こどもたちは 貝殻かいがらを 集あつめています。
The children are collecting seashells.