I've been looking for a complete data set to build a water pollution map from. So far, it's not been easy to find for free. I'm sure it's out there somewhere. I'm assuming you want a "fresh water pollution map" as it would relate more to a traveler in the form of "drinking tap water considerations". Is this right?
I ask because you do mention the Gulf of Thailand, which may mean that we want all the salt water included as well. That would be a bit of customization, and beyond just countries as we'd have to define where the divisions are for salt water bodies.
What I have found is one good data set but it didn't include enough countries to be of much use for this project. Others I found are related but not specific enough information to be of much use. I'm looking to find a set of at least 150 countries in the sample.
Also found several premade maps as go-by's that are related yet not quite what I need.
Making the maps is the easy part. The research and/or finding the documented research is the real task.
I think I am thinking about beach life and where are oceans a problem.
Drinking water is always a problem also.
The map would seem to work for both problem, drinking and finding nice islands.
There may need to be a few new areas to point out here in the US for that map as well...http://www.waterpollutionlawyers.com/
It looks like we are designing new ways to pollute our own resources.