It is this green stuff:
Olympus Stylus 1s, 300mm, ISO200, f5.6, 1/250s
No, I don't mean to say peat bogs are made of frogs, it is just there for decoration, and probably wondering why it can't swim here.
What makes a peat bog is peat moss (Sphagnum). It grows in shallow water, and it can absorb a huge amount of water. The lower parts die off, sink down, and form peat. The top bits grow on.
The little plants can reach a great density, forming a layer small animals can walk on, and there even are some plants that grow on top of this layer, like sundew (Drosera):
Olympus Stylus 1s, 300mm, ISO200, f5.6, 1/250s
Peat moss also turns its surroundings acidic, limiting the number of species of plants that can grow near it. This acidity also preserves the bodies of mammals that fall in, hence the well-known bog bodies that are sometimes found in the peat, like the famous Tollundmannen:
This photo is the Public Domain
I have seen his face up close in the museum in Silkeborg, Denmark, and apart from the skin colour, his face looks like he is just sleeping, even though he died about 2000 years ago. It was a very powerful experience to look at him.
This experience also made me walk carefully when I take photos in the peat bog. I wouldn't mind ending up in a museum, but I'm not quite ready for it yet.