( Warning: Contains many spoilers, although truth be told it probably won't matter much. )
I caught this while channel flipping one day, and it provided a reasonable amount of entertainment.
Even with a summary, the plotline is sometimes borderline incomprehensible. ( How the heck that iceberg managed to stay intact, make it's way to the tropics, and how that bird was able to get Lars back home is beyond me. ) We never really know what the fudge is going on. We don't know what the thingybopper is that's taking the fish, and they never tell us. So in terms of a cohesive plot, this movie absolutely bombs.
That's a shame, because the animation style is quite appealing. It's nice and soft, and easy on the eyes. The machine did succumb to shotty CG work, but it's not too incredibly glaring.
The characters are pretty good, but not the most fleshed-out. Lars is loveable, as is his little seal buddy ( though he does get a bit irritating at times ).
Overall, it's a pretty enjoyable, fun movie, but its major fault is that it seems to have been dumbed-down a lot for the kids. Tsk tsk tsk, shame.