This is one of those things you think nothing of until the obvious is pointed out to you.
The DEC says hitting golf balls into a Lake or River is illegal and you can be ticketed. Others say it's disrespectful and dangerous.
Golfers tend to take out old golf balls they'd never use anymore and whack them into the water. It's something those living waterfront, who also golf, do. They've done it for years. Sometimes those balls wash back up on shore and they hit em again.
I'm not sure the threat of a ticket/fine will stop people, but the story from David Figura of NewYorkUpstate.com should make people at least think.
There are practice balls that float and biodegradable balls on the market as well. Figura's story says cruiselines use those balls.
Good thing this doesn't count for water on a golf course, or else the DEC would just follow me around and make enough money to support the entire Region 6 operation up here.