I very like "Figure 4 Typical Kt design curves for a semi emerged low crested reef breakwater" in this publication.
It is a relation between the wave transmission Coefficient, Kt and wave heights in flume for a submerged reef constructed of mega geocontainers - 3 wide.
You may find interesting the following paper although is not directly referring to geotextile breakwaters: 'Numerical prediction of performance of submerged breakwaters', Ocean Engineering, 32(2005), 1235-1246, Rambabu & Mani