The green on the trees is the Guck you gather. The Crypts are slimey black/green stone block small buildings that are easy to miss except for the two green torches at the gates. Some Swamps have none, some have a couple, some have lots. I have found three Swamps on my Map and only one Swamp has Crypts, about 5 of them. There is alot of exploring that needs to be done for everything. Make sure to level up your swimming cause you'll be sailing alot.