Light in the sea

I was interested in this display at Maryport Aquarium. If the top 200m makes up 25% of the oceans, then the oceans cannot be as uniformly deep as I'd imagined. The detail on the absorption of  different light colours is exceptional. I recently found out that ABSORBANCE = log10(intensity in/intensity out). If only 20% of light has reached 10 metres, the absorbance = (1/0.2) = 0.70.