I would like to use a kind of classical handwriting font and to transform the "F" and the "S" in two waves.
The 2 bars of the "F" could become a double wave (a small underneath and a bigger one at the top) while the "S" would be a big one.
As a very distant influence, you can have a look at this painting:
https://en.wikipedia.org/wiki/The_Great_Wave_off_Kanagawa
Of course, the logo will need to be easily readable (sometimes handwriting fonts are not very readable).
I pick only 2 style inspiration because they where the only one I found were the logo is included in the letters.