If Marlin and Nemo are the father and son with the bad relationship in this movie, the sea turtles—Crush and Squirt—are the parent and child pair that everyone wants to be.
Marlin first meets Crush while cruising along on the East Australian Current after he saves Dory from the jellyfish. Crush admires Marlin's chutzpah in battling the jellies, but also shows the clownfish dad that part of being a parent is letting go of your kids:
MARLIN: Oh my goodness!
CRUSH: Whoa. Kill the motor, dude. Let us see what Squirt does flying solo.
SQUIRT: Whoa! Whoa! That was so cool! Hey dad, did you see that? Did you see me? Did you see what I did?
CRUSH: You so totally rock, Squirt!
See what he did there? Crush knew that Squirt had gotten into trouble, but instead of rushing over and saving him from failure, he gave the little turtle a chance to solve his problem on his own. And Squirt was super psyched because he achieved something on his own. Nice fathering, Dude.
And really, if you're going to take parenting advice from anyone, it would be an 150-year-old sea turtle, right? They've seen stuff. That's why Crush shares this nugget of fatherly wisdom with Marlin:
CRUSH: Aw, it's awesome, Jellyman. Little dudes are just eggs, leave 'em on the beach to hatch, then coo-coo-ca-choo, they find their way back to the big 'ol blue.
MARLIN: All by themselves?
MARLIN: But, Dude, how do you know when they're ready?
CRUSH: Well, you never really know. But when they'll know, you'll know, you know?
This is deep.
Marlin's run-in with Crush and Squirt is just another step on his journey to being a way better dad. He realizes that one of the mistakes he made with Nemo was not trusting him. He didn't believe in his son and didn't challenge him because he was so scared about what might happen. Crush helps Marlin move past his fears about become way more chill.