The surfer-dude sea turtle in 'Finding Nemo' is Crush. He is a laid-back adult green sea turtle who meets Marlin and Dory in the East Australian Current.
Crush helps the pair navigate the powerful current while Marlin searches for his son. His relaxed attitude contrasts with Marlin's anxious, overprotective personality. Through their conversation, Crush encourages Marlin to trust Nemo and allow him to become more independent. Crush's son, Squirt, travels with him and appears during the same sequence.
Crush speaks in an exaggerated surfer style, using casual expressions and calling Marlin “dude.” The character's scene also gives the audience a playful introduction to ocean currents and sea-turtle behavior. In the film, Crush is voiced by director Andrew Stanton, who originally recorded the dialogue for a story reel. Test audiences liked the performance so much that Stanton kept the role.
The wrong options are other important marine characters. Bruce is the great white shark who leads a fish-eating support group, Gill is the Moorish idol in the dentist's aquarium, and Squirt is Crush's young son. Only Crush is the adult surfer-style turtle.