WHen i used to mine in 1.7 I could see all the torches i left wayyyyy down. Now i can only see about 2 torches. then the tunnel just goes dark. I have draw distance set to far.
Did you turn the light level up? While I generally have it set on the default "Gloomy", I'll periodically put it up to "Bright" when placing stones deep underwater. It's really the only way to see the ocean floor at the deeper levels.