Yep, right on. I only sighted young whale sharks, not more than 4m.
Diving in Christmas Island - highlight was the whale shark, other than that excellent coral cover, clear waters (30m). Fish diversity not as high, although there are some endemic Indian Ocean fish species. Dive service pales in comparison to Indonesian diving, and very expensive as well. Of course, the land offers other highlights - red crab migration, robber crabs galore, get up close to seabirds...
All in all, a well rounded experience.