What activity would my GSD be good at? Any suggestions?

I have a 16 month old, small (55 lb), female rescue GSD. She has a lot of energy, more than that could be solved with a daily walk. I really want to do some type of activity/competition with her. We are looking at agility because she is super fast, nimble, agile, and can jump very high! She is very smart and can learn to do almost anything. She has pretty much no fear! She also has a high prey drive, and is very workable. I want this activity to tire her out because of all her energy. Is agility a good choice? Seems like a lot of work but is it worth it? She currently is at training classes so she is fairly well trained, not so sure she could be an obedience or rally dog, needs really fast pace. Oh she also loves water! What are some things she might be able to do?