Dissertating and other such words

I know someone working on their PhD. She insists that the process of writing her PhD is "dissertating". You can't just make up words like that. You write a dissertation. You don't dissertate!

This is the same person who uses the word "cohere". I will admit that it is a word, but I will not agree to use it.

This weekend, I heard a word show on NPR that discussed collective nouns. I learned that one would say:

• a smack of jellyfish
• a charm of finches
• an exhaltation of larks, and
• a blabber of radio hosts (not true).

What I don't know, is why you can't just say, "there's a smack in the ocean". Why do you have to say, "there's a smack of jellyfish in the ocean"? If 'smack' implies a group of jellyfish, isn't "a smack of jellyfish" redundant? This question was not answered.

I also learned that James Lipton, of Inside the Actor's Studio fame, wrote a book titled, "An Exhaltation of Larks" about collective nouns.