Dunk's cousin Mo comes to visit everyone in the reef, because he has a sunburn from spending too much time sunning himself above the surface. Looking to get as far away from the warmth of the sun as possible, the kids take Mo down to the Arctic, but he quickly realizes it is too cold for him there. / Splash and friends are having a great time pretending to be different fish, but Finny isn't good at pretending she is a fin whale because she is not used to using her imagination. Together, the kids teach Finny how to have fun harnessing the power of her imagination, while also learning about fin whales.