ECOM-si is a 3D ocean circulation model developed principally by email@example.com Alan Blumberg of HydroQual. It is similar to the Princeton Ocean Model (POM) described in Blumberg and Mellor (1987), but incorporates an implicit scheme developed by firstname.lastname@example.org Vincenzo Casulli for solving the gravity wave so that the need for separate barotropic and baroclinic time steps is eliminated. ECOM-si is not generally available, but if you are looking for a freely available 3D circulation model for conducting research in the coastal model, I suggest checking out either POM or the very nicely documented and maintained Rutgers/UCLA ROMS model. Note that POM and ROMS are not available for commercial use. More information about modeling applications with ECOM-si can be found on the HydroQual web site.
We have also developed an extensible software system for storing, analyzing and visualizing the model output from Blumberg/Mellor type circulation models.