Full 50/50 (Upper half land, lower half water) Island style
Split 50/50 (Left half land, right half water) or (Back half land, front half water)
Partial 33/66 (Full water with a small land area)
Partial 66/33 (Full land with a small pond area)
less than that... and I imagine it would be considered a terrarium with water, or an aqua-scape with a protrusion and not a paludarium.