The eel is a fish with a long, serpentine body, distinguished from the serpent by its tail and fins (though, sadly, these are frequently omitted in period art). It’s usually found in heraldry for the sake of a cant, as in the arms of di Pescera, mid-15th C. [Triv 288], the civic arms of Ahlen, 1605 [Siebmacher 220], or the arms of Ellis, 1610 [Guillim1 168]. Eels may also be called “congers” for canting purposes; small eels are also called “grigs”.
Eels are naiant by default, their bodies wavy. See also sea-serpent.
Gregoire le Gris bears: Or, an eel erect embowed counterembowed, a chief embattled azure.
Osweald Hæfring bears: Gules, in pale two eels naiant Or.
Magdalen Mwrray bears: Azure, two eels haurient respectant Or and in chief a roundel argent.