There's a little house with a deck by the water adjacent to Penitence Bridge. Drop down there to find this.
In west Otisburg, you'll find this green panel on a building. Using the Batmobile's Forensics Scanner on it will cause Riddler marks to appear. These will lead to a weak wall on a construction site in Ryker Heights - you'll have to perform a leap over a winch-able ramp to get there - which you can blow through to reveal a trophy.
There's a crumbling building near the edge of the island. Grapple up to it to find a trophy.
On the eastern side of the area is an Urbarail track. Zoom in to spot a cracked portion and shoot it with the Batmobile's cannon. Grapple or glide into the hole to find a trophy inside.
There's a Riddler puzzle right near Penitence Bridge. You need to guide the trophy ball to the prize slot by using the Remote Electrical Charge in conjunction with the Batmobile's winch. The path is pretty straightforward - just remember that differing pulses from the Charge repel or attract the ball.