Continuity mistake: In the first 'Ice Age' Diego isn't afraid of water (in the beginning he chases the woman and the baby through the river before she jumps off the waterfall and never shows any fear) but in this one he suddenly is. It's not like that he is just afraid of swimming because in the second movie he shows fear anytime when he touches water.
Plot hole: At the end of the movie, when the water drains away, there would be no way for a) the amount of water to drain away that did and b) for the mammoths that came through to be completely dry. (01:16:20)
Trivia: The movie contains a spoof of Saving Private Ryan, where Manny is hit by a geyser and temporarily loses his hearing. Incidentally, the German voice for Manny, Arne Elsholtz, also synchronizes Tom Hanks, who also stars in that movie, which creates an inside joke by happenstance in the German version.