Hey Barrabart,
Agree with everything here. I don't have a cruiser, but the Pathy is a v6 petrol. I don't have a snorkel because I've never been into really deep water and haven't really needed it yet. The R50s breathe from right up the back of the inner guard, which is normally high and dry. That, and a can of WD40 are what I put my trust in.
About the only other water-diving tip I can give is to stop before diving in and let everything cool down. No real point for little creeks, but anything hub eight or deeper I usually stop for 5 mins to have a drink, let the brakes, diffs, etc all cool down a shade before diving in. But you're no doubt well aware of that trick.
That said, I've been tempted lately to fit a snorkel just as cheap insurance. As the others have noted, it's not foolproof, but it does give a good increase in security for the motor. If you do get one, if you have it fitted make sure they know it's to be fully sealed. I've heard too many horror stories of brand new Patrols and R51 Pathfinders that are running snorkels, but they're not sealed. The owners assume since they have a snorkel, and that it was professionally fitted, that it will be up to snuff, whereas many times it's not.
Good luck!
Matto