Seal rivet holes?

I'm getting ready to install an X-Wing mount on my new kayak - will be my 1st run of drilling into it.  question being, what is used to help seal around the rivets?  The guy at astoria scuba got me set up with the rivets with the plastic gromet thing on them, i want to add some goop to get a solid seal around them when i'm done though.  thanks in advance, i'll post up some pic's when done.

That's what I have done. The goop is a must with all the penetrations in my kayak. It has worked well.
You will probably here other opinions on the rivets.

Good luck

Marine Goop.

lol, i didn't realize Goop was a brand of...goop.  i'll have to hunt some down, thanks!

Decided against rivets, in the event i decide to ever take the rail system off.  went with size 10 stainless machine screws instead.  came out pretty decent - now just to rig it up with depth finder, and pole holders.