"What's wrong, Sally?" Cora said.
"I was protecting my egg case," Sally said.
"But then a huge wave came.
It swept away my egg case!"
"That's terrible," Mo said.
Sally bit her lip. "I lost my babies!"
"Don't worry." Cora hugged her.
"I can find your egg case."
Mo nodded. "Cora is the best helper!"
"Follow me," Cora said.
Everyone swam to the compass.
Cora shot her ink, and the shell opened.
Inside, the picture showed a rocky cave.
Sally's eyes went wide. "That's Riptide Cave."
"What's Riptide Cave?" Mo asked.
"It's a bad place," Sally whispered.
"Why is it so bad?" Mo asked.
"Some fish told me stories," Sally said.
"Sometimes the cave pulls you in.
Then you never come out again!"
"What?" Mo said.
"Don't worry, Mo," Cora said quickly.
"Those are just stories.
I'm sure we'll be fine."
Suddenly the arrow took off. Whoosh!
"Let's go!" Cora said.
She and Sally started to swim.
But Mo didn't follow them.
"What's wrong?" Cora asked.
Mo was shaking. "I'm . . . scared of that cave!"