Amazon Light PAR Question

[LifeOfAquatics]

for the below light, it said on the second to last image it has 100 PAR under 24 inches of the light. But it said OPEN AIR, not water. Would the par basically be the same in water not including rocks? or would it differ? thanks!

 

[Gtinnel]

According to BRS it is not the same. The reasoning they gave was that there is some light that gets reflected off the surface of the water.
I've never personally tested it, but the reasoning they gave seems logical to me.

 

[Evo R]

The short answer is no. It will not be the same.

"open air" has almost zero resistance. Where as water has loads of different molecules and particles that hinder and slow down the penetration of the light waves. Hence lots of resistance.
In fact PAR drop off grows exponentially as goes deeper down.

BRStv has loads of vids on youtube about PAR ratings and depth ect.