PAR readings

[Scythanith]

LED readings are usually only about 5-10% off in my experience. Each colour spectrum is different. You can find the articles and proper calculations to adjust an apogee sensor on their website. Not sure about the Seneye though.

I'd say 160 is quite low on the water surface. I get anywhere from 450-800+ at water's surface with Mitras and T5's (about the same height as you).