1. Run around in town and try to spot Deserter Agitators who mostly stand next to normal guards:

Talk to five of them and go through their dialogue. Be careful sometimes they turn aggressive and attack you. When you are done, turn the quest in at Calia Hastings and get the follow up.

2. Go to the ship which is furthest to the south of the Theramore docks and clear your way through it until you reach a room that looks like the captain’s cabin:

Loot the boxes there and clear your way out. Turn the quest in at Caila Hastings and wait until she performs a little script, then get here follow up.

3. Talk to 6 Theramore Guards and go through the dialogue with them. Go back to Caila and turn the quest in. Get the follow up.

4. Now first swim or waterwalk to the little island with the light tower (72,47), right east of Theramore. Turn in [35] This Old Lighthouse at Babs Fizzletorque and get the follow up.

5. Swim directly south to the docks of Theramore and dive under them. There you’ll see Young Murk Threshers. Kill them until you have 4 Thresher Oils.

6. When done, swim a little east to (76,55) where you should see a boat. Clear your way inside and go down the set of stairs which leads down from the deck. Instead of continuing straight, go down another set of stairs:

There you’ll find Gavis Greyshield along with a guard. Kill them both, Gavis won’t die but he’ll turn friendly at some point and you will get a quest complete message.

7. Swim back to the island with the light tower and turn your quest in and get the follow up. Swim to the Theramore docks. Turn in [35] Dastardly Denizens of the Deep at "Dirty" Michael Crowe, get the follow up [36] Is it Real?. Then turn in [37] The End of the Deserters at Calia Hastings.

Repair/sell junk.

8. When done swim southwest of Theramore to (58,60) where you’ll find Nat Pagle. Turn in [36] Is it Real?, get the follow up [37] Nat's Bargain and look in your inventory for some fish paste, use it.

9. Swim southwest to a wrecked ship at (56,62). A lurking shark will attack you, kill it and return to Nat. Turn in your quest, get the follow up [37] Oh, It's Real and return to Theramore. Turn in your quest at Major Mills. Now careful, when you get the follow up a script will start:

In front of you a sea monster will spawn and attack the city. You’ll have 12 marksmen helping you shoot the monster BUT you are not supposed to fire at him with your own weapons. At the docks you’ll see canons which will become useable once the monster attacks for real. Basically your only job here is to run between two of the 3 canons and alternatively fire them at the monster until it is dead. You should be able to get the monster down easily before the marksmen are dead. Be careful of his water stream though, it pushes you back and you’ll have to run back to the canons.

10. When the monster is dead (really nice script) you’ll get some fireworks and you can turn in your quest at Major Mills.