Alex awoke feeling strange. Belatedly, he realized he was lying at the bottom of some water. Yet he wasn't suffocating. He lay there a while, simply taking in the fact that he was still alive. He tried to move his arms and legs, but found that he couldn't locate them. His body moved strangely. It took him a moment to realize that he wasn't him anymore. He wasn't even humanoid. He was just some kind of a gooey blob at the bottom of this water. Like some kind of sentient jello.
His movement was limited, but he found he could slide along the bottom of the lake, sea or river. What ever he was in. The slid over dirt and rocks and all kinds of underwater plants and flowers. When he slid over them, he found he could dissolve the plant matter into his body if he chose. It felt strange. It wasn't exactly taste, but he did receive detailed information about the things he consumed.
A fish swam by overhead. It swam near him for a moment, curious about what he was, but as soon as Alex reached for it, the fish shot away. Yet in its wake it left its flavor so to speak in the water. Alex didn't need to consume the creature to understand it. Tasting and seeing it with his sightless sense told him a lot. How it was structured. How it moved.
Alex didn't mean to transform. He just did. Suddenly he was a fish himself. His goo body changed form and size and suddenly he was swimming through the water. What was going on!? He now had all the fish's senses and abilities, including his strange 360 degree sense.
Flitting around the water as a fish was fun and interesting, but Alex had no intention of staying as a fish for the rest of his life. With a bit of experimentation, he found that he could almost instantaneously change back and forth between being a slime and being a fish. He categorized several more creatures in the what he now realized was a lake. Several more types of fish, a crab and a frog. The latter two would at least get him out of the water. Maybe he could find a better land animal up there to become so he could actually figure out where the hell he'd ended up.