Elly, Tash, and Sierra are off on a whale-spotting adventure!

But when one of Sunday Island's freak storms rolls in, they're tossed into the sea, and Tash's precious boat, The Mojo, is shipwrecked.

Stranded on an island, the girls put up a flag in the hope of being rescued.

But they're not the only ones who need rescuing - the whales have swum too close to the beach and the calf is stuck in shallow water.

While Sierra sings to it to keep it calm, Tash and Elly construct a raft to float the calf back to its anxious mother.

As the reunited whales swim away, the girls sift through the driftwood that's been washed up by the storm.

Why is there so much? Donning snorkels, the girls investigate, discovering a beautiful underwater world of starfish and coral.

But the sun is sinking in the sky, and they still haven't been rescued.

If nobody knows where they are...will the girls have to spend a night under the stars - alone on a deserted island?