Hi Amy,
I'm sorry to tell you that you won't find much of substance related to Octonauts at Walt Disney World. You may find a tee shirt or plush character for sale in the merchandise shops, but there is currently no themed room, ride, or other attraction related to this program.
There are, however, other Disney Junior representatives at WDW, particularly at Disney's Hollywood Studios. The Disney Jr. Live on Stage show features characters from the shows Mickey Mouse Clubhouse, Sophia the First, Doc McStuffins and Jake and the Neverland Pirates. Additionally, several of these characters can be found in a meet & greet outside the attraction. Be sure to check the free Times Guide when you enter the park for the schedule of when they're available.
Additionally, you can find Disney Junior characters at the breakfast and lunch seatings at Hollywood & Vine seatings at Disney's Hollywood Studios. Characters are subject to change, but recently have included Little Einsteins' June and Jake, as well as Handy Manny and Special Agent Oso. There's yummy food in a fun environment.
Please let us know what else you need to plan your vacation. We're happy to help.