We have ported the support for Selafin files in Crayfish plugin:
www.lutraconsulting.co.uk/products/crayfish/
The release will be in a couple of weeks, but you can access the source code here:
github.com/lutraconsulting/qgis-crayfish-plugin
and build it for your platform.
The plugin is extremely fast compared to one other TELEMAC2D reader plugin we tested against.
If you have a small sample test model, feel free to do a pull request so that we can use it for our unit tests.
Looking forward to your feedback/comments.
Regards,
Lutra Consulting