There is an actual name to these things but I can’t remember what it is. When rocks in rivers and lakes are sticking up above the waterline they sometimes will get covered with snow and form these little white bubbles which look really cool! In a fast-moving river, the rocks act like anchor points in the photo. The eyes will stop on these rocks and be a place to rest. If you go to black and white, then these rocks are a great contrast to the rest of the river.