So, dumb question.... are you able to actually see bottles on the river floor, or are you just sort of feeling around? Also, are you using scuba gear or snorkeling?
I've never done either but from what I've read I can tell you, all of the above. Sometimes the water is clear and you can see the bottles, sometimes the bottom is muddy and you have to feel around. Sometimes it's shallow enough to snorkel, sometimes you need scuba gear. I've always wanted to get into diving for bottles but I don't have enough money and I can't swim very well. So I have no imminent plans to get into diving for bottles.
Sorry I have been away from the site for a month or so, Thanks Rick for the comment. I am gettin the Cordial Gin back this weekend I sent it out to be cleaned and I sold the other two. I will post a photo when I get it back. Shmoo you can see the bottles depending on the visibility under water. Mud diving is just feeling around under the silt. Its kind of not fun as you cant see and up can be down or vice versa. Its just a great hobby that keeps you in shape you can do it year round mostly, I usually stop in summer as there are two many yahoos boating, fishing, and in some fresh water bodies bacteria levels can make it unwise to be in. Being a good swimmer is always a plus as #!it happens and you may need to ditch your gear and weight belt and swim a ways to get back on dry land. Snorkeling is a great way to start out.