Any of them can be done without a guide.
Here's the questions to answer:
Do you know the current at the site?
Do you know where the current changes on the site?
Do you know how to navigate back to the entrance?
Do you know you'll return to the entrance?
A group I was with last April decided to try Cai together, without a guide. We had a very experienced instructor on the dive, I'm an AI, and the other 2 divers in the group are average experience. After 20 minutes of diving at Cai, the instructor had 1500 left in his tank and the other 2 divers were close to 1000. We had seen grass. Sand. A few fish. That's about it. 2 days later I dove the site with Bas Tol
BAS Diving. We did the site twice, once in late afternoon and then a night dive. Both dives were 2 hours, we saw everything from turtles to seahorses to black brotulas to baby drummer fish to octopus...the list was nearly endless. We saw tons of the site, had 2 awesome dives.
YMMV but without a guide, the east coast is hard to dive. The sites aren't marked, the entrances can be a beast, the currents change within the same dive, and unless you know the landmarks and the places to turn as well as the compass headings to take, you just won't enjoy it. Bas is well worth what he charges, he's safe and he knows the island like few others. I was gung-ho to dive without a guide, especially given that I've got 4+ hours of dive time on the rebreather to navigate and recover from getting lost, but I'd rather spend my time having fun and Bas makes it fun.
