He can be contacted with the NPC Contact spell to find out about when the next trip of the fishing trawler will be. He also is the NPC that you can obtain a Sextant from for coordinate clue scrolls after speaking to the professor in the observatory.
This article on an NPC has an associated dialogue page. Click here for a transcript of possible conversations with this NPC.
Before Murphy referred to both male and female players with "my son". However this is no longer the case. Instead he refers to female players with m'hearty.
Murphy breaks the fourth wall, by saying "Game Magic".
Humorously, if you attempt to dive with a pet cat in your inventory, you will have a funny conversation about making a cat-sized diving suit. You will still have to store the cat, however.