The first two sentences quoted are correct; a gerund phrase and a noun phrase can exist together and you can also have noun phrase with noun phrase and gerund phrase with gerund phrase. Your third sentence is incorrect because you are saying "the act of capturing its crew" (by way of the "the" in front of the gerund) and therefore needs an "of" between "capturing" and "crew" or you need to delete the "the".
or:He received a medal for sinking an enemy ship and
thecapturing its crew
He received a medal for sinking an enemy ship and the capturing of its crew
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