Fido, those are called power poles and what they are is a shallow water anchor that stabs in the ground. Ostensibly for breezy days or where there's current and you want to stay in one spot. Those give you stability too.

I've never used one personally or been in a boat woth one so i couldn't vouch for how they work or don't work. One thing for sure, is people seem to like them! They're everywhere these days.

BKB