Fallout 4 created by Bethesda Game Studios.
Images used for educational purposes only.
Main Walkthrough

Forest Grove Marsh is located in the west of the Commonwealth. You’ll find it on the northeast side of the large intersection of highways just west of Diamond City. You are most likely to come through here during the quest Reunions, though you just skim along the edge of the small community.

Forest Grove Marsh looks like it used to be a small town, but has now, obviously, been flooded by its titular Marsh. There’s a lot of water hereabouts that will keep the number of enemies to a minimum, but that same water will also stymie your search efforts to a degree. RadAway ain’t a bad idea if you’re not in Power Armor or don’t have the appropriate Perks.

You can expect to see and find the following in Forest Grove Marsh:
  • The waypoint is pretty much centred on a Pub. The inside isn’t that special, though there’s a closed room behind the counter on the main floor with some meds. Watch out for an explosive attached to the door.
  • Head down the hill into town. Pretty much every house down here that’s on dry land is boarded up and useless. Boo. That said, there’s an Eyebot wandering around here that will tell you about the Cambridge Polymer Labs and put them on your map, which is… something. 
  • The only building of real use, in the north, looks quite gutted, and has multiple floors; you can find a decent amount of ammo inside, including an Advanced level floor safe behind the counter with yet more ammo. Climb to the roof and you can find a steamer trunk of goodies, a Caps Stash, and Sheila’s Holotape.
  • If you look along the west side of town before hitting the water you’ll see a wrecked-out car with some boards attached to its top. This leads to the roof of an adjoining house, and eventually into the flooded area of town, if you keep following the rooftop pathways. Out here you’ll start seeing Ghouls prowling the streets, and I recommend using this spot to take them on. You can snipe them from up here or just draw them onto the narrow planks for a bottleneck effect. Either way, better that than fighting down in the water.
  • There’s only one further use for Forest Grove Marsh itself at this point, and that’s to collect the Mutated Ferns that grow on the rooftops. Solomon, a vendor back in Diamond City, wants a sample of these flowers, and will pay money to you for fetching him one. If you’re a sneaky non-combat character you can probably grab one of these without engaging the Ghouls down in the water at all, which, given their numbers, might be preferable.
  • There’s still one thing you can do ‘round these parts, that said. Just north of town is a dam, which you can reach by following the boarded paths. The dam itself is not terribly exciting, and you’ll find a few items wandering around on top. (Don’t jump down into it. You’ll probably get stuck, particularly if you’re in Power Armor.) Cross the dam to the east, though, and you’ll see Relay Tower 1DL-109 jutting out of the landscape. Activate the Tower to discover several distress signals in the area.