Hey folks, looking for a bit of insight.

I’m shooting with an Olympus E-M10 Mark IV in a Backscatter Octo housing, using dual Sea & Sea YS-D3 Duo strobes. I usually stick with RC mode, which limits me to a max shutter speed of 1/160 sec. That’s generally fine, but in bright conditions with clear water, I sometimes want to bump up the shutter speed to darken the ambient light and get a nicer, deeper blue background.

Would HSS (Super FP mode) be a good option here? I know I could switch the strobes to manual, but I’d rather keep using RC if possible.

Anyone tried this setup or have thoughts on how well HSS works underwater with this gear?

You could get to 1/250 sync speed in manual flash assuming your trigger co-operates. If you are using a fully manual trigger I know the more advanced bodies like the EM-1 MKII can get to about 1/400 sync speed. I don't know if the AOI trigger will allow that, the Nauticam trigger achieves it by not reporting as a flash to the camera, just using the sync contacts.

HSS is a possible solution but you lose flash power with it, the YS-D3 strobes have plenty of power so should cope OK up to 1/250 - 1/320 range.

Another thing you could try is using the extended low ISO of 100 if you haven't tried already, the strobes should have enough power to deal with that and it's equivalent of going from 1/160 to 1/320 for background water colour at the same aperture. You lose a small amount of dynamic range from this but you should not notice in most circumstances.