Ocean is the Default "NotLand" biome. Afaik you cant change that.
If you whish to have a "Custom Ocean" that Acts as Ocean. Just modify the Ocan.bc
Otherwise you only get rid of the Ocean if you make use 100% Land.
# Land rarity from 100 to 1. If you set smaller than 90 and LandSize near 0 beware Big oceans.
# Land size from 0 to GenerationDepth. Biome groups are placed on this.
Maybe you need to tweak LandFuzzy aswell.