Key Difference: A waterbug is an aquatic insect that belong to the order Blattaria. It is an insect that is found in water bodies like lakes and rivers. A cockroach is a black or brown colored straight winged insect and it belongs to the order Blattodea. A cockroach is quite similar to a waterbug. Cockroaches mostly stay in land, whereas waterbugs mostly stay in water.

Many people confuse between the two and think that they both are same. However they both are different types of insects. American cockroaches live in sewers and therefore they are often termed as water bugs.

A Waterbug, as its name suggests, lives in or on lakes, ponds, streams or any water body. They look similar to cockroaches in many ways. They have an oval shaped body. The front part of the body is large. They have piercing mouthparts and with the help of these mouthparts they suck the body juices of small fishes, insects, etc. They have two legs in the front that are known as pinchers. The pinchers are used to stab the pray. They can grow up to four inches. The water bugs that spend most of the time either swimming through or walking on water, are considered to be the true water bugs.

Cockroaches have a broad to flat body. They possess hard and protective pair of wings. There is also a delicate inner pair of wings that is used for the purpose of flying. Eyes are quite prominent and compound. The size of an adult cockroach ranges from one-half to four inches long. Cockroaches have been around since the time of dinosaurs. A cockroach can live a long time without having any food and this period can extend upto 31 days.  A cockroach can also survive about two weeks without any water.

Some of the prominent differences are listed below in the table:-

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