Take in any extra rode you can by motoring up on the anchor, then tie the line off on the cleat, have your mate stand back and motor the boat past the anchor. The boat can put considerable strain on the anchor, more than most hooks can take so be careful. If you have to power the hook up in the vicinity of coral you are probably hurting something pretty. No matter what type of gear you've selected the first objective to consider is how to make the boat stay still without smashing anything pretty or ecologically sensitive The corals and other sealife have enough trouble surviving with poor water quality, they shouldn't have to worry about us battering them with our ground tackle. In the shallower depths it's a matter of looking for the lighter colored areas, in the deeper spots the color difference is more subtle but nonetheless visible.
Polarized sunglasses work wonders.
In fact when you get accustomed to using sounders you can conceivably identify sand by sounder alone. If there are other boats anchored in the area the task will be easier, if not, the fist thing to consider is the wind. The next thing to think about is the current. Short of an educated guess the thing to do is look for a t rap buoy floating, or something similar. If there is a current it will leave a wake, this will identify the direction and give an idea of the velocity.