i'd agree with kubajzz, try and find a way to tile it. it's hard to find any sort of image much bigger than that, to be honest (at least in my experience - anybody know something i don't?), and the likelihood of finding one that's got the same texture but at a significantly larger size... slim. on the plus side, it looks like a really nice texture, and it goes really well with everything else in your scene, but i agree that the waves want to be smaller.
unless you say it's a miniature world right down near the ocean surface, so even a little wave looks quite big? random thought...
- colclough