Tonks could say it was an amazing feeling until she turned blue in the face, it wouldn't change the fact that Oliver would no longer be doing that which he loved most in the world. Those who can't do teach, maybe, but he intended on being one of those who could do for as long as possible. He didn't want to think that his stride was already over in his mid-twenties. It would be horrible; Oliver had no desire to be known as the youngest Keeper to be fired from professional Quidditch, even if he got to teach.
But as much as he didn't want to do that with his life, somehow, knowing that there were other options made it a little better, a little easier to bear. He knew he couldn't play Quidditch forever - no one could, no matter how fit - and it would be fair to try to postpone that moment as long as possible... But even yet, when time caught up to him, there would still be other options. There were other Quidditch options, even if it wasn't playing. Oliver repeated that to himself a few times, but even still, it left a sour taste in his mouth.
Tonks did have a point, though. He wouldn't stop working at it. He didn't believe himself capable of resenting the game he loved so much simply because it made him work, however. But he worked so hard already... Something about the finger trailing down his neck was very reassuring, very convincing, though he tried to shut that door before it opened too wide.
"Yeah, we can swim," he said with a smile, not thoroughly convinced it would help and definitely not over his need to assert himself in the name of Quidditch, but still somewhat mollified. "I shouldn't be alone to swim?" he asked with a smirk. "And why not, I'm a big boy."