These waves on the Great Lakes are a lot more destructive than they would be in the ocean. The wave periods are much shorter which means that instead of 8 or 9 seconds apart , they are 3 to 4 seconds apart. That makes a 25 foot wave in Lake Ontario about as destructive as a 40 to fifty foot wave in the open ocean.
On the ocean , 5 or 6 foot waves usually means that you go up and down without the waves cresting or breaking into white heads. they are just long rollers. In the Great lakes a six footer will hammer you around one after the other in quick succession and make you want to get off the water quick.