For those who don't know, these are airdrops which are normally hard to reach, but since this part of the city is submerged unless you fix that up later in the game, you can just swim from one spot to the next, there are no enemies. Item drop range is level 7-9, western ones are a bit higher level.
To do this, you have to get to the safehouse marked as 1, from where you can just swim to the 12 drops marked on this map:
Approach the safehouse from the north-west. If you try it from the north east there will be toxic shit and enemies.
Start it in the morning, since you can't use immunity-boosters in the water, and you don't want to swim 600 meters to do that in the middle of your collection run.
Get as much stamina as you can to facilitate the swimming, along with a load of lockpicks.
You only need to pick the airdrops once, after opening them the content respawns but they remain open.