The tub is one of only two 4-cell still lifes (the other being the block) and was discovered by the JHC group in 1970.
Adding an extra cell to one of the corners results in a boat, while adding two to opposite corners results in a ship. It can also be seen as a long-1 version of the barge.
Two mechanisms for a tub acting as an eater are known, though rarely applicable. An example of the former is the Eureka shuttle. The other mechanism involves the tub acting as a rock; an example is 5blink. This can be generalized to a large number of still lifes including a tub-like protrusion (e.g. boat, loaf, cis-hook with tail).
The tub is also occasionally useful as a simple induction coil for a row of 5 cells: see e.g. airforce.
The tub is the fifth most common still life in Achim Flammenkamp's census, being about a quarter as common as the boat but only slightly more common than the pond. It is also the eighth most common object (and the less frequent of the two 4-bit still lifes) on Adam P. Goucher's Catagolue.