Before I purchased them I saw a video on YouTube where the posters mentioned they were sealed and placed the units inside their overflow box. I have them on the outside of my tank so I wasn't concerned but by my visual observation, they appear to be submersible.
Great wave pump by the way. Dead quiet, easy to clean and makes a lot of flow. I use two on a 50 gallon pentagon with one in reverse flow. I had MP10's but all three I have owned has suffered ceramic shaft failures.