RedactedNarrative: O1 and P1 were navigating on Big Stone Lake in V1 near Skeleton Island near the rearing ponds access area.  PFDs were available in V1, but O1 and P1 were not wearing any during the accident. O1 stated that V1 was traveling less than 10 mph.  O1, P1,V1 was navigating near Skeleton island and O1 struck a submerged rock with the lower unit of V1.  O1 and P1 navigated V1 back to rearing ponds access areas with V1 and looked at damage and noticed propeller damage and lower unit damage.