Yes Aquaman is really strong. He is even "OP" But unless you know what your doing he is shit.
Rush Psi. You can switch between AD buff and AP buff to get a good steroid on your abilities. Remember more of your abilities scale off of ap so that's why this build is more focused on AP for mid. The items are very self explanitory. Basically its pure damage and pen with he DRDD for the mana suatain.
Your q has the best poke at long range. So try to poke from a little ways back. Just more damage coming out. E second makes it easy to dodge poke and sustain. To sustain health just e through minions basic then e back and basic.
Teamfights are fun. You w ult is AP, which is stupid when you build FULL AP aquaman! His w ULT combo is dirty. The most effective initiate is the Q ult. Once you hit your trident youll dash to the target with your ultimate. W's ult is a big burst that goes off of the enemies missing health. Only use it as a finisher.
Your e ultimate is a third dash that flips any enemy behind him. That is only good for close range initiate. Thats aquaman mid. Enjoy!