Cleanliness of the water, both sea water and drinking water does not seem to be a problem.
The sea water on the east side of the island is certainly clean and clear.
I don't think you want to swim on the lee side of the island for a variety of reasons. Not the least of which is that we saw a crocodile sunning himself in the mud on the side of a pond during our first visit four years ago.
In the past, we could drink tap water with no problems. However, the Belican Beer distributor just south of town will deliver beer and softdrinks by the case and drinking water in a 5 gal plastic jug. Just call them or stop by and order. They will deliver to your hotel or condo. Very reasonably priced. Good luck!
WASA is on the south side of town. We live down that way and drink the tap water no problem. Once in town..No way. The old pipes will make you ill if you are a gringo. Anything south of Blake street and you should be fine.
Not to be the voice of doom, but Dr. Marioshi did have a study of the waters(both fresh and salt) done about 2 years ago. During his brief tenure working for Green Reef, my ex-roomate David found that there was indeed E-Coli bacteria in the waters off the reef at the south end of the island near the dump...the Green Reef report should be available if you wish to look into it.
All I can tell you is that I've had the local tapwater from Capricorn to Banyon Bay. No problems so far. As for swimming offshore, unless I was immediately east of the plant, I wouldn't give it a thought. Can we say "a spit in the ocean?"
How could the statement "there was indeed E-Coli bacteria in the waters off the reef at the south end of the island near the dump.." possibly be true when the dump is located across the island on the far western shore?