A few years ago I used the Hartenberger 625TTL and 250 hs TTL with a Fuji S2 pro in a Subal housing and was very satisfied with the quality of Hartenberger.
I switched to Seacam D800 with 2x Seaflash 150 but my wife is still using the Hartenberger 625 with the Fuji S2. (analog TTL)
For information I am selling the Hartenberger 250 hs TTL with 2 reflectors 4500K and 5000K for 900€ because we have to many strobes . see link below