First divie in a quarry

I just finished my open water dives, which happened in an old quarry. Apparently the algae just bloomed, and I literally could not see 10 feet away. Its about the most frightening thing. There's little comfort in knowing that many people dive at the quarry and there is nothing that would kill me, but not being able to see anything is just such an uneasy feeling.The dive instructor told us to swim towards the wall and follow it around the quarry so we could make sure we weren't floating up or down. Well you have to find the wall first. Many times when swimming towards it, the water would be a light green color and just start getting darker and darker as you got nearer. In the water you don't know how close anything is (Especially when diving the first time) and many times I could not tell if I was still in open water or if I was about to slam into a wall.A tree had just fallen over the water the night before, and our dive master brought us under it. Again the water was a light green, then immediately got dark. Then you could see the branches and looking up you could see the tree in the water. There was no surfacing at this point as the tree was blocking the way. It just gave me the heeby jeebies.