wave action ideas anyone?

[Corvette Reefer]

I recently got a external pump that's about 300 gph and i plan on making a 2 way into the tank i was trying to get a idea of how to get wave action without buying a OM or SCWD any ideas of what i can do to get some good wave action? my tanks 20 gallon tall and yeah any other if needed ask. I thought about making my own OM type thing but yeah what r ur guys ideas to do so.