If you are missing the one that is under the first bridge, you can still go back
Hover from one of buildings to the edge of 2 containers standing on top of eachother, you should be able to reach the top. If not, you will end up between them and can jump on top of the second one. Drop down and you notice that the game is trying to stop you from progressing (like it sometimes does when you are trying to follow a set path). There's a easy way to prevent this, just keep on jumping. And oh, you can also walk through containers. When you reach the second stop, just before the cutscene where they start shooting you/Zeke, you need to go back a bit and jump on top of the container. Jump over the fence but start hugging the wall. Jump forward until you can reach the area where the cutscene takes place and you will fall through the ground and end up in the section where the cutscene ends, under the bridge.
I think that that shard is unmissable though and you can jump near it without bugging yourself if you backtrack from the bottom too (but you can't go around the fence).
I suggest that you check the platform near the train station near Zeke's place in the sea, or the tallest building in the Ground Zero for a shard that you can't see in the map.
Whoops, forgot what you were asking about. You don't have the skill to do the first trick, but there shouldn't be any other difficult ones in the first island than the one in the broken pier. Just run around the place mashing R3