A shower radio is a battery-powered radio that is waterproofed to allow it to be used in a bathroom or other wet environment. Some versions also include a CD player and/or a clock. Shower radios generally lack headphone jacks and AC adapter ports, which could short out or electrocute the user. For the same reason, they also tend to lack external antennas.
The first mass-produced shower radio was patented in 1985 by Andrew R. Mark, of Stamford, Connecticut.[1] The product was marketed by Salton Inc. under the brand name Wet Tunes. There are varying designs; some are meant to be hung from a pipe or shower rod, while others can be stuck using a suction cup or something similar to the wall of the shower.
There are a number of different types of shower radio they are either analogue or digital. More recently a water-powered radio and windup radio designs have been produced to completely remove the requirement for batteries.
Source: http://www.showerradio.org.uk/shower-radios/types-of-shower-radio/ Types of Shower Radio