Well, the events of the first chapter went "downhill" fast. It started with a mystery, which is good. The concept was original and interesting, the ending a little rushed. Overall, it was good, I really liked it.
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Maybe this kind of story should be extended into a complete novel because I think that there is plenty to write about. There are many things to explore such as scientific research, disagreement/clash with fellow researchers and the resulting feelings, like 'is the research really going to succeed', 'can I really do this?', There might be high risk involved should the research fail, like the death of a loved one if the cure is not developed, or a promise made to somebody. If the research is given some kind of urgency, then it will justify the main protagonist's insistence to continue. The emotional struggle caused by the transformation should be explored, human emotions clashing with the rising amphibian instincts: the morality of killing vs satisfying hunger, the good feeling of having heightened senses vs losing the protagonist's humanity (second thoughts), guilt after killing the lady friend then internal struggle and maybe rage and destruction. The story might then end in many possible ways, self-sacrifice in order to compensate for the destruction caused; accepting the transformation, but getting killed by somebody; or surviving, but having to accept the new self; and so on.
These are just some ideas, in case you need them. In my honest opinion, this story deserves more, it has substance, but not enough space to develop. It lacks character development and emotion (internal and external struggles of the protagonist) which is somehow understandable since it is a short story. The writing style was good, the grammar and punctuation spot-on. I noticed that the author researched the science involved in the story well, which is a good thing. Keep experimenting, you are on the right track!