波が来るよ! 大きいぞ!
Here comes a wave. It's a big one!

 ビーチサンダルは?
Where are your flip-flops?

 知らない。
I don't know.

 ビーチサンダルなしじゃ、砂の上歩けないわよ。
You can't walk on the sand without them.

 タオルなしで横になっちゃ駄目! 砂だらけになっちゃうよ
Don't lie down without a towel. You'll get sand all over yourself.