A:
It is there to create more of a splash when you jerk the bait. Water can come in through this hole and is then ejected out through the "gill" areas of the bait.
I have used these and caught fish on them although they are not my favorite walker they still catch fish! For the price it is a great addition to your aresenal. Just be carefull with what you throw them at. Docks and other hard objects seem to take their toll on these baits. They could be more durable but like I said, for the price they are worth having.