Currently my game needs a top ocean view. Can this ocean effect done using box2d? or should I dive into write my own physics (liquid/water simulation). Ideas and suggestions are welcome.
Physics and appearance are completely different things. I suppose you mean the latter, so Box2d cannot help you, as well as any other physics engine. The simpliest approach is to make an animated water tile and just fill your surface with it. This texture can also be generated procedurally if you want (for example, using noise algorithms). It is quite simple to implement and applicable to both 2d and 3d.
Speaking about water physics, Box2d and most of other physics engines do not support fluid dynamics. However, if you only need simple things like inertia and acceleration, they can easily be achieved with Box2d, because in this case you just need to tweak bodies' parameters.