It's not the cigarette butts which are the only form of litter that would benefit from not being discarded into the sea, but also your packets!
This image was taken on a reef several kilometres from the shore and only accesible by boat. Whether you, your guides or the crew, it is the responisbility of all of us to try to prevent this.
The funny thing is that when we look at the gross picture, you and the divers on the boat have done much more damage to the ecosystem over there, than the poor guide who discarded his cigarette packet in the sea. I include myself in your boat, as I am not much different than you.
So true, but then that is the cost of tourism. The trick is (i guess) trying to mitigate againest this by being a responsible diver.