The world gives a nice vertical element to Kingdom Hearts, even if Sora seems a little slower than normal. The ocean world breaks up the style of gameplay enough to give a new and interesting gameplay. But it seems like people don't like it much, why is that?
The main reason I wasn't the biggest fan of it was because the layout felt confusing. I remember as a kid getting lost in there trying to figure out where I need to go.
Otherwise I didn't have much issue with it.
Yeah there is that one place toward the end where there are cave passages with different water flow directions. It can be confusing to figure out which way to go.