Shape file fill area

Hello, I have two files and I need to display them. The ocean data is in netcdf format while the coastline is a shapefile. In the first image, I am using mapshow() to display the coastline on top of the ocean. Mapshow() fills the area between the polygons in yellow.

The problem with mapshow is that it is time consuming. When I try to use the fill(), it does not fill the area. Any ideas how should I fill the area without using mapshow?

I decided not to use mapshow because it is taking a lot of time.