This is an Early Build with him going Power Damage, which makes his E a bit weak in comparison to his other attacked (E is Attack Damage, while most other abilities are Power Damage).  It does however give him a true Hybrid damage style, unlike most hybrid heroes that sitll go strictly Power or Attack

Aquaman excels as a Laner who gains some fun gank abilities when he gets his Ult.

His ability to harras and do some nasty early damage with his Trident of the King (Q) is amazing.  Putting early levels in this gives the damage a nice boost, however the will cost is rather taxing.  The range on the Trident is amazing, can go through obstacles, and does more damage the further it travels (double damage from min to max distance).

The Gank combo of Q>E>W>R>E>Q is crazy in a solo or teamfight situation.  

Also to chase the Running Straggler from a teamfight, tag them with a Q (Trident of the King) then Ult to dash to them followed by W to Trip them.