Squiglet is a monster who lives in a plain white world, which he populates using a magic crayon. Squiglet uses today's straight line to squiggle a cat called Kitty who's wearing a lovely hat. Her uncle, the pussycat who went to sea with the owl, gave it to her so she can feel brave. And she needs to be brave so she can go on an ocean adventure like he did! Then she can see all the underwater creatures - like starfish and octopi. The trouble is, Kitty's having a hard time finding her way to the seaside. Squiglet can help - by squiggling it for her! Soon they're standing on a jetty, looking down at the water. But Kitty still doesn't feel very brave, especially when a wave splashes up around them! Suddenly, the wind catches Kitty's hat and blows it out to sea! Now she'll never be brave! Squiglet thinks he has the answer and squiggles a fishing rod to hook it out! But just as Kitty casts the line, the wind blows her hat even further out until they can't see it anymore. Just then, a whale called Walter pops up! He's seen Kitty's hat underwater! Now how will she get it back? A look at the squiggle pad gives them the answer - a submarine! And Squiglet can squiggle one. He and Kitty climb aboard and follow Walter down into the depths. Walter's friends, Sally the starfish and Octavia octopus, direct them until they find Kitty's hat caught on some seaweed. Walter rescues it and hooks it to the submarine's periscope and soon Kitty's back on dry land and wearing her hat. She's sad to say goodbye to her new friends - but she has had an adventure. And she met all sorts of underwater creatures - just like her uncle.