There seems to be an direct relationship between how colorful the duck is and how skittish they are. Ring-necked ducks are pretty mello and laid back. They are often seen cruising in small groups, especially in the lower impoundment.

Male Ringed-neck

Female Ringed-neck

Click on the image to see a larger version to see where they get their name

Ring-necks in flight

Female stretching

Thankfully he's fast, lest she drown
On the other hand, the pretty boy Wood Ducks are some of the most skittish ducks at Great Meadows. On rare occasions you will see them in open water close to shore. More commonly, you will hear them flying away as they see you before you see them. Keep your eyes pealed for them swimming in among the reeds. Don't be surprised if you do see one sitting in a tree.

Male Wood Duck

Side by side comparison of male & female Wood Ducks

Male Goldeneyes

Male Bufflehead

Male & Female Bufflehead

Male Mallard

I forgot I had taken this shot, until I got home and was reviewing the photos. I like how it looks like the female Mallard is shaking off the water like a dog
These is a pair that can often be seen near the observation deck. They appear to be getting somewhat habituated to people, so they have been swimming closer to shore....of course that may also be because they feed in shallower water.
Hopefully they will decide to raise a family here this year. Since they are cavity nesters pay attention to our many dead trees, or perhaps they will set up housekeeping in one of the many duck boxes.

Male & Female Hooded Merganser

Male Merganser showing off

Though they are somewhat habituated to people, they really don't like it when you approach them too rapidly / closely or talk too loudly which unfortunately two people did while I was photographing them. Thankfully I kept my eye to the camera and got a couple of flight shots as they left to find a calmer, quieter spot.
Updated: To replace accidentally double posted photo with the correct photo.