viewed a show the other evening about the condition of the oceans & coral reefs around the world.
From the Gulf of Mexico to the Great Barrier Reef pollution is damaging this resource.
local pollution & agricultural run off are responsible for the coral degradation.
Fertilizer is a big issue .. Huge 'dead zone' at the mouth of the Mississippi due to agricultural run off.

what are the reefs like in the andaman sea? Is any of Thailand actually on the andaman sea?
straits of malaca? would include Krabi & perhaps Phi Phi.
Gulf of Thailand?
I have always avoided Pattaya's water & never been to Samui.

Phuket's water seems to be rather clean, but I doubt one can see excess potassium.

I'd hate to see an analysis of the Chao Praya's water .. I do not eat prawns in Bkk because of the prawn farms in the Chao Praya's flood plain.