Looks like it ends in "dai" or is that just part of the waves?
Feel with your fingers along the edges of the picture and especially on the highs and lows of the waves, to see if you can feel the lumps and bumps of oil paint. It would likely be done on canvas, which you could see on the back side. Maybe wood if it is older. If it's a print it will be smooth on the surface. Oil paintings have a thick, sculpted feel to the paint and it is even applied with a knife in places. Your edges along the bottom look painted, I would expect to see a smoother edge line if it was a print.