Need help plugging up flush mount rod holder. Suggestions? :)

[kayaKANG]

Hey guys,

Newbie kayak fisher here. I bought a used ocean kayak prowler 15 and it has two flush mount rod holders already in the back of the hull (I hope I'm using the right terminology here), but I noticed that the rod holders have holes at the bottom that empty right into the inside of my kayak. Is this normal?

I know there shouldn't be too much water getting in via those rod holders...but does anyone have suggestions for how to plug them up? I tried fitting some foam golf balls in them but they're too small for the size of the hole.

Or is this something I shouldn't worry about? Pictures attached so you guys can hopefully see what I'm talking about...thanks!