cofferdam vs caisson

cofferdam and caisson both are nouns.

Word	Noun	Adjective	Verb	Adverb
cofferdam	Yes	No	No	No
caisson	Yes	No	No	No

As nouns, cofferdam and caisson are synonyms defined as:

cofferdam and caisson: large watertight chamber used for construction under water

Other synonyms of cofferdam include pneumatic caisson.

cofferdam (noun)	caisson (noun)
large watertight chamber used for construction under water	large watertight chamber used for construction under water
	an ornamental sunken panel in a ceiling or dome
	a chest to hold ammunition
	a two-wheeled military vehicle carrying artillery ammunition