Not all motors have head bolt holes that punch through into the water jacket, and not all head bolts on a Holden 6 or V8 go through to water either..

Howver, on the head bolts on Holden motors that do go through to water, I prefer to use a thread sealant (like Loctite 567) as it not only removes the risk of water working it's way up the thread helix, but it also prevents corrosion of the threads, and the problems that could cause down the track.