None of them had slept well. They had taken turns at sentry duty, though there was little to guard against.
Sheel stripped to the waist. She passed the rope through a belt loop on her shorts and Bobb tied a knot to secure it. “I’ll try to do this on my own power, but if I start tugging pull me back in right away.” She dived over the edge before they could acknowledge.
Away from the shore, the water was clear, with sunlight penetrating deep before beginning to diffuse. Closer in, a soup of algae swallowed the light and restricted the view. Sheel swam into the thick green water. She passed under the shadow of the shore and the temperature dropped.
Groping around, she found something firmly anchored. Tugging on it brought her in close to a thin root, with another just beyond. Pulling herself from root to root, Sheel worked further under the floating island. Up ahead, the roots became thicker, wrapping and twining together in a criss cross pattern. Small fish swam through the gaps, feasting on the algae. Something dark trailed into the depths. There was no way she could get close enough to examine it.
There was a movement, just at the edge of view to the left. Sheel turned her head to see a large dark shape leaping at her. It was as long and thick as her arm with teeth upon teeth and tiny eyes ringing its mouth. The fish ran up against the net of roots, jamming part way through one of the larger gaps. Now it was trapped. It thrashed and thrashed, becoming sluggish as water stopped flowing through its gills. Smaller fish darted in to take nibbles out of the predator. Chunks of flesh floated off to be wrapped in algae.
Sheel kicked away, aware of the pain in her lungs. She broke the surface with the opposite of a cry, the painful sound of great gasps of air. She lay on her back in the water, revelling in the sun, as Gim and Bobb dragged her in.
Under the tree, with the first of the purified water at her lips, Sheel explained what she had seen. “We’re sitting on an ecosystem growing on a giant plant. There is a root, from the tree, trailing into the depths. I don’t know whether it’s attached to the bottom, maybe it’s just a trailing anchor. There are smaller roots branching off near the surface, and the algae has coated itself to these. The dead stuff’s building up over time to make this, ‘soil’. The roots drape down below, knitting together to make a net of sorts. The net catches larger fish, smaller fish feed on the corpses, breaking them down for the algae and plankton, and the tree feeds on the nutrients provided by the single celled animals.”
“But can the system support humans?” Bobb wondered.
“I guess we’re going to find out.”