I'm not 100% sure how to port to SFM, but if you can get me a tutorial I'll try.

SFM maps require HDR Lightning, If this map has it, I think you can just port it to SFM.

@Super Chief
The map already has HDR, if that's the only requirement just extracting the map from the gma and putting it in SFM should do.

Actually got it to run in SFM with only a few issues.
TF2 textures override the boathouse floor. Don't think anything can be done with this.
Glass in the boathouse gives error textures.
Glass in combine underground area shows generic reflection and isn't see through.
Water is black.

Aside from these, the map is completely functional.

I'll work on fixing up a version for use in SFM with those problems fixed. Thanks for notifying.