Adventures of the Little Seahorses

The triplets and six other seahorses and two jellyfishes are going to the coral reef! On the way they meet Big Jelly, a jellyfish they have once rescued, and Katarina tells her about a very secret notebook that she owns. They then discover that Toddy, Katarina's shark friend, needs fingernails for a medicine. Can Katarina get the fingernails? And what has Big Jelly and the notebook got to do with it all?