bog - quagmire - swamp - reservoir

bog ciénaga, pantano [soft, wet ground]: The water level in the bog varies only a few inches during the year.

boggy pantanoso,-sa: a boggy patch

quagmire /ˈkwɒgmaɪə, ˈkwæg-/ ciénaga [similar to bog, and you sink into it when you walk on it]: The streets were a quagmire of mud and manure.

swamp /swɒmp/ pantano [an area covered with water]: I was lost in an alligator-infested swamp. ^ The swamp stretched out for miles.

reservoir /ˈrezəvwɑː/ pantano [natural or artificial, for water supply to the population]: The water piped from the reservoir was so polluted and sullied that it was of little use.

marsh / marshland (also marshlands plural) pantanal; marisma [a wet area, often flooded]: There are areas of marsh and grasslands alternating with rocky cliffs and outcrops interspersed with stretches of acacia woodland and rocky hillsides.

fen / fenland (also fenlands plural) pantanal, zona pantanosa [especially in the east of England, similar to marsh]: The bog is dominated by acid-loving plants belonging to the heath family, while the fen and swampy wood lack species in that family.

mudflats (plural) marismas: The old man moved across the mudflats to the edge of the sea.

lagoon /ləˈguːn/ laguna (costera), albufera: a tropical lagoon ^ Nearly 3,000 civilians waded across a lagoon to escape from rebel-controlled territory to government-held territory.

muddy place / mudbath barrizal: We had to plough through a mudbath to cross over.

quicksand (also quicksands plural) arenas movedizas: I hopped onto a solid-looking sandbar and promptly sank to my knees in quicksand.

pool charca: They were fishing in a pool.

rainforest selva tropical: In West Africa, 90% of the indigenous rainforest has gone.