"Destiny may be a clumsy swimmer, but she has a big heart. She has a big everything, actually — whale sharks are the biggest fish in the sea. Destiny resides in the Marine Life Institute, where one day an oddly familiar blue tang named Dory falls into her pool. Destiny is admittedly embarrassed by her obvious lack of grace, a product of poor eyesight (very near-sighted), but Dory thinks she swims beautifully. And Dory is delighted to learn that her super-sized friend speaks whale, too. Destiny and Dory used to talk through pipes when they were little."
Destiny first appears when Dory is tossed into her enclosure and upon seeing her, the near-sighted whale shark almost crashed into Dory as Dory asks Destiny to know if she could find her missing parents Jenny and Charlie. When Destiny continues talking to Dory about her missing parents while swimming with her, she constantly bumps into a wall and tells Dory that she cannot swim and see very well. Dory then instantly makes friends with Destiny by complementing her on her swimming. As she thanks her in the emphasis of speaking whale, Destiny also speaks whale to her as she also realized that she and Dory are friends when they talked through pipes when they were little. Dory then asks Destiny to know where she was from, in which Destiny says that she is from the Open Ocean exhibit, which is where her parents would be. Dory then asks Destiny to know if she could take her to the Open Ocean exhibit, but Destiny tells her that it is not possible for a whale shark to go to the Open Ocean Exhibit. As soon as Bailey the beluga appears and tells the two to keep it silent, Destiny tells Dory that Bailey thinks his echolocation does not function properly, due to his head injury. Destiny then tells Dory that there is nothing wrong with Bailey in which Bailey's ability helps him find objects far away in which she tells Dory that his echolocation is still "healing".
As Dory, Bailey, and Destiny talk about echolocation, Hank suddenly jumps into the exhibit and finds Dory and tells Destiny to give him the tag given by Marine Life Institute volunteers to bring him to a permanent aquarium rather than releasing him back to the ocean again. When Dory tells Hank as she forgets to know the exhibits where are parents would be at, Destiny and Bailey tell Dory that they would be in the Open Ocean exhibit. Destiny then tells Hank that the way to get to the Open Ocean exhibit is to go through the pipes in which Hank can't fit through the pipes and Dory must go there by herself in order to get to the exhibit. Upon reaching the surface, Dory tells Destiny, Bailey, and Hank to find a plan how to get to the Open Ocean exhibit. Destiny and Bailey are seen again to help Dory and Hank find a way to get to the Open Ocean exhibit by doing a big splash. As Dory sees Destiny jump, Hank tells him that this is the signal to get to the Open Ocean exhibit as he tells her to follow the signs leading to the Open Ocean exhibit.
Destiny and Bailey are seen again when they hear Dory through the pipes who is looking for her parents in the quarantine area of the Marine Life Institute while Destiny tells Bailey to use his echolocation to help Dory find her missing parents in which Bailey says that his echolocation couldn't function properly as Destiny tells him to use his ability harder. Bailey then tells Destiny that he can seen the quarantine area as well as Dory by using his echolocation; Bailey and Destiny tell Dory to listen to them by choosing the said directions to help find her parents in which Bailey tells Destiny that two fish (Nemo and Marlin) are swimming from the other directions in the pipe while Destiny tells Dory to choose the other direction to avoid colliding into Nemo and Marlin, confusing Dory as she meets up with Marlin and Nemo, in which the two did not see the two clownfish at first. Destiny and Bailey found out that Dory is safe when she encountered Nemo and Marlin.
After Dory found Jenny and Charlie in the kelp forest of Morro Bay, she then tells Destiny and Bailey that she found her parents. As the two hear Dory, they manage to escape their exhibits by jumping into the ocean. As Dory, Charlie, Jenny, Destiny, and Bailey plan to stop the truck containing Marlin and Nemo inside, Bailey sees some otters as he crashes into a pole and Destiny crashes into him. Upon encountering the otters, Dory asks Destiny to flip Dory when the truck passes through the bridge so the otters can bring her safely. As Dory tells her parents that she would be safe, Destiny flips Dory over the bridge as the otters carry her safely as she tells the otters to stop the passengers with their ability to cuddle with each other. Destiny and Bailey are later surprised that the truck (still with Dory, Nemo, and Marlin inside) went away. Destiny and Bailey later see the truck falling into the ocean, freeing all the fish from the truck. During the epilogue, she, along with Bailey, and Hank, help tutor Mr. Ray's class
Destiny appears in the 2016 revamp of the attraction Turtle Talk with Crush. In this revamp, Dory tells Crush to know if Destiny can tell the guests if they can speak whale, in which she agrees to. Destiny and Crush tell the guests how to speak whale. After repeating what Destiny says in the emphasis of a whale, an actual whale appears while Destiny and Crush warn Dory that the whale is approaching. After Dory is stuck between the whale, Crush tells Destiny to know how to ask the whale to leave, in which Destiny and Crush tell them to do the same whale call again so the whale can move away and save Dory. Upon doing so, the whale moves away and this saves Dory.
She might be the reason why Dory can speak whale, even though she's not a true whale, but rather a shark.
The way Destiny jumps from her enclosure is a reference to the famous climatic scene from Free Willy.
In a different version of Finding Dory where Jenny and Charlie also had short-term memory loss, Destiny was their adopted daughter, and there would be a sibling rivalry between her and Dory.