Buoy in a boat

I admit that I know nothing about boats, and I hope that it is a buoy! I googled and it looks like some of the images.  :-)
I usually see these between a boat and the dock when the boat is moored.
Mixed results from the start of the season for Kalyn's volleyball team. On Thursday, they lost to Northwest Nazarene in three straight sets, and this afternoon they beat Central Washington in three straight sets. They played so much better today, great to see them recover from the first loss. Kalyn played great today, 9 kills, 6 blocks and 1 ace.