Toward the end of the movie, when Hercules is talking to Hades about saving Meg,he sort of KNEELS down and reaches into the river of souls (when his hands shrivel up). However, once he decides to go in after Meg, he certainly does take a BIG DIVE into that river, doesn't he?
Take a look at the river of souls. Ever pay attention to the fact that they are spiraling ever downward at a pretty good rate if you look at the scenes just before. Also, Herc takes his time making this deal with Hades. Meg sank pretty deep in my opinion.
Kodiak
What he's pointing out is that the river of souls is much further down from the ledge when he dives than when he first reaches down to it. When he first reaches down, it's not far from the ledge at all (he can reach it) but when he dives, it's much further down to the 'water'.