Technical notes: Manuel would have been breathing oxygen at the same pressure as the surrounding water. His lungs would not have imploded.

In the first paragraph, I’d suggest changing ‘higher atmospheric pressure’ to ‘higher pressure’. There is no atmosphere.

In the 2nd paragraph, ‘oxygen composition’ should be ‘oxygen content’ or, if you want to get very technical, ‘partial pressure of oxygen’. I’d also suggest changing ‘poisonous’ to ‘fatal’.

In the 4th paragraph, ‘colleges’ should be ‘colleagues’.

AH! Dang… they’d only implode if he ascended rapidly past pressure changes, right?

Thanks regarding other fixes!!!

Other way around. Holding one’s breath while ascending causes overexpansion of the lungs, a Very Bad Thing. ‘Explode’ is too extreme a word. To be honest, ‘implode’ is too extreme as well. ‘Collapse’ is more accurate.

Other notes on second reading: (a) The word ‘expelled’ in the first sentence is grammatically wrong. I think ‘was expelled’ would be better if it was forced out, or ‘escaped’ if it was the sylph’s idea. (b) Verb tenses seem to fluctuate between present and past. The first 2 sentences in paragraph 2 illustrate this. © ‘Entered a panicked state’ seems unnecessarily convoluted when ‘panicked’ would do just as well. (d) "He could feel a pain entering his lungs’ similarly seems like too many words. ‘His lungs hurt’ works well. (e) ‘Symbiosis via the rebreather’ is, again, convoluted. In this case, the entire phrase could be deleted with no harm. (f) In the 3rd paragraph, ‘reformed’ is not the word that I would have expected.