Try this: chain multiples of 23 as wide as you want the blanket to be then skip first 2 stitches, one dc in each of next 10 stitches, 3dc in next stitch, 1 dc in each of next 10 stitches, skip 2 stiches and repeat. For the next row, chain 3, skip next stitch, dc in next 9 then carry on with the pattern. If you want more (narrower) waves try 5dc/3dc/5dc skip 2 instead of 10dc/3dc/10dc skip 2.
It's one of my favorite patterns. I learned it from my Grandma. I've used it so many times I can make a blanket in the dark while I watch a movie.