Regarding the sharks, it's fairly unusual to see the lemons, except on the feedings. My mother (whom I took last year) was VERY shark fearful due to a diving incident in the 60s. She wasn't going to go snorkeling, which she adores. By the end of the trip, she was looking forward to seeing the sharks.
You will see black tips almost every dive. They're everywhere. But they're extremely well fed and not at all interested in you. Same with the lemons. On the black tips, after the first couple dives when I got used to them being around, I started to think of them as little puppy dogs. They just did not seem that shark-like. They were more cute and ever-present - big fish with teeth but not aggressive. The lemons were definitely sharks with shark "attitude", but they cruised around and didn't come near, except at the feedings. And then they knew what they were after. If you follow the instructions, you can have really good experiences there. HIGHLY recommended.
But no, there aren't typically that many sharks around as you'd think from that photo.
Can you tell from this thread and the other I *really* liked French Polynesia?