Guild Wars 2 Halloween 2012 Mad Memoires Part 2: Friendship

Site 1 – Dig deep in muck, where all the garbage of Lion Arch flows.
Head to the Northwest corner of the Grand Plaza, and head into the water. You will find a moored at the docks. Just dive into the water and look under the pier. You will find an underwater sewer entrance. Follow it forward to the intersection. From here turn downward and follow that tunnel. You will find a number of shipwrecks to navigate around. Just keep moving forward, you are on the right path.

Location of Samson for the Mad King's Shadow

You will want to use the scanner again when you reach the final hunk of hull in the cavern. Swim upwards from there and use the Aqueous Scan, if someone else is not around. This will reveal Samson. Talk with him to get the Mad Memoires II: Friendship:
Samson: “Me, Os, and Ewan had a secret hiding place down here. I used to train with the Thorn brothers. I liked Ewan best, but Os could be funny sometimes. If only he hadn't fled that day in the sewers.”
Hero: “What happened?”
Samson: “Ewan was sick, so Os and I went looking for trouble, just the two of us. It was fun until giant wurm latched onto me. Os didn't even draw his sword. He just ran.”
Hero: “Thank you for your story. I'll make a record of it.”

This will give you the Mad Memoires II: Friendship “In which a friend joins young Oswald Thorn for the adventure of a lifetime.” It also has a the hints:
Site 3 – Say more now and look more where Kryta's descendents are buried.
Site 4 – Go to the hills and set down black roots in stagnant water.