He stayed underwater for as long as he could, but his body wouldn't allow the peace to continue. His mind wouldn't allow him the release that was not thinking about his best friend. He didn't deserved it. He didn't deserved to live his life like nothing happened when Wally West was dead.
He went above water gasping for air, knowing he willingly stayed more than he should. The public poll was empty at that time of night and that was exactly why he choose it. He could be left alone with his pain, without having to deal with people. They always wanted to talk, to ask how he was doing, to make sure he was okay. He wasn't okay and he wouldn't be. His friend was dead and Dick couldn't shake the feeling it was his fault.
He was leading the team while Aqualad went undercover in Black Manta's organization. He was responsible for the lives of everybody related to that mission and he couldn't do anything to help his friend. He had to watch his life being taken away so he could save the world one last time.
How could he be a leader again after that, after losing one of the most important person in his life? How could he trust himself again when he couldn't protect the one guy who quit the hero business in order to live his life?
Dick was supposed to be used to losing people. He lost his parents when he was a kid. Other heroes died since he became Robin and then Nightwing. But something about being Wally, the redheaded kid who ran around him, tripping in his own feet, talking more than anybody could ever keep up with, made his heart stop beating from time to time. It was as if he didn't have the energy to do so, because there wasn't really a point. Why would you keep going when you could just die like that, no explanation, no goodbyes? Why keep pretending to make a difference when you can't save the people who means the most to you?
At the same time, Dick felt pretty ridiculous about how much he missed the man. Wally had parents, he had a girlfriend who lived with him and they were all moving on. They were still in pain, yet they remembered and honored his life the way they were supposed to be; moving forward. Artemis was even back at being a hero in the team he created and led.
Dick didn't need a lot of soul searching to figure out his problem was beyond accepting the fragility of the human life and how even people with superpowers didn't live forever. His problem was he didn't know how to live in a world without Wally West. A life of protecting people is a life of tragedy, it's a life of lost and loneliness and he chose this life knowingly. He could count on his fingers the amount of people that knew his secret identity, maybe even less the ones who knew who he truly was; the boy behind the mask and the fight, the man who still dreamed about his dead parents and wish they were there, the man who looked at his mentor and knew that for better and for worse, he could never be like him, the kid who only ever wanted the people he loved safe around him.
Dick knew then he needed to learn how to be Richard Grayson without Wally West being his friend. Without him laughing at the stupid jokes and rolling his eyes at the calls asking for advice when he did something idiotic to his girlfriend. Without having that person he could tell everything to and not be afraid of being judged or reprehended, because the person would have his back no matter what.
Richard Grayson didn't lose just his friend, he lost part of himself, a part he wouldn't never have back. Now he just has to learn how to live uncompleted. He needed help.