I have just returned from Vietnam (August/Sept 2010) and of course did the obligatory Halong Bay 3 day 2 night boat trip. The scenery is absolutely beautiful but I was so distressed by the pollution levels (air and water) that I am not recommending to any intending travellers.
The water in the bay we kayaked to for swimming was extremely polluted (althought the small beached area was relatively clean. After swimming, my skin stung for the rest of the day. Maybe the sea is extremely salty...or maybe the little mounds of oily foam floating all over the water are a testament to who knows what chemicals being dumped into the bay.
The sky was so hazy that there were no stars to be seen at night and the islands were invisible until you were almost on top of them.
The depth of the physical pollutants in the ocean was a real shock. For as far down as I could see (bear in the mind the water is pretty clear) there were plastic bags. Add to this the plastic water bottles, fishing flotsam and jetsam (including nets and floats), bits of broken up foam, all manner of food packaging etc etc and you get the picture of where this World Heritage Site is heading.
I asked one of the crew on my day boat about it and he said it mainly comes from the fishing villages (where he lived incidentally). When I asked if anyone came to clean it up he just looked at me bewildered. Obviously the idea of cleaning it up is completely foreign.
On reading the other reviews on here, it seems the problem has compounded in a few short years. How much longer are the authorities going to wait before this site is completely destroyed??