oil is a denser medium or water is a denser medium

 

 
density of pure water = 1000 kg/m3
density of sea water = 1022 kg/m3
 
different oils have different densites.  
 
example:
 
density of coconut oil = 924 kg/m3
 
density of olive oil = 800 - 920 kg/m3
 
density of glycerine = 1259 kg/m3
 
density of crude oil = around 850 kg/m3
 
most of the oils has density less than water. 
viscosity of oil is always greater than water not density.