Royal can be a fun open water dive if conditions are clear. I had fun swimming around it several times. The cavern zone is ok I suppose, but the cave is one of the most dangerous ones I've been in. Creepy as heck, too. The last fatality was a double, and they didn't recover all of the equipment...when I found equipment buried in the silt matching the description of that missing from one of the deceased, I put it back carefully and got the heck out of the cave. I don't think I'll ever go back. It's a silty place, no fun at all, bad kind of silt.
I know you can open water dive safely without a cavern or cave certification, but as usual I can't blame the people who jump to conclusions too much. Plenty of people without self control.
Besides who wants to dive solo and have to pay for all of the gas at today's prices? Get a buddy and split it!