Clustering data based on shapefile

I need to cluster my data based on where it falls on a shape file. I have a shapefile of continental shelf and the data has been plotted onto this using longitude and latitude. The data needs to be organised so that data that has been collected on the continental shelf represents one group of data, and the data that has been collected off the continental shelf represents the other. How would I go about organising my data based on the continental shelf line?