It has a long extendable neck, a long and spiked tail which ends with a net, it does not resemble any of earths animals, it is also known to be able to swim. In an original treatment for Walt Disney's Alice in Wonderland, it was depicted with a long body with a net attached to its tail. In the 2010 film, it is shown as a colossal creature resembling a cross between a rabbit and a talking bulldog. But its appearance can not be confirmed.
Voice of Bandersnatch(2010 film): Joan Honacker