Computers don't "store" electricity. They store information on transistors, which can be read or rewritten when electricity flows through them, but don't lose their hard-written information when the power gets shut off. Humans supply power from outlets when they need to read it, just as these creatures would supply power from their bodies when they need to read it. However, a transistor is a complicated thing.
Water isn't as conductive as you think it is, and makes for a poor battery. Electrosensitive animals in real life sense only magnetic fields generated by the flow of electric impulse through nervous systems, as well as the waves of electrocommunicative animals, who generate wave signals by oscilating their voltage.
Binary takes a lot of coding, and without microtransistors, anything encoded via electricity would take up a lot of space. You can't differentiate much more than north or south pole, positive or negative end, potential/voltage difference, or on/off state, most of which are binary, and putting any of them near each other (except for on/off, with transitors), merges or cancels, destroying the information.
For example, to encode information based on voltage difference, each character or word would have to be a separate circuit with a different volt power supply, which would have to be spaced far enough apart (and require constant power) to prevent connecting through air or when the creature touches them, as if connected the circuits join and have the same potential difference. A book of magnets held in different positions would try to tear itself apart, and the magnetic fields of all the magnets would eventually realign to be the same anyway, destroying the information, unless they were kept far apart, and the pages very thick, making for a very large book indeed.
All of which is far more complicated than just simple engraving for texture, which can be accomplished with a rock, a tentacle, and another rock. Read by feeling the grooves and bumps with the skin. Becomes ubiquitous form of writing, because people discover it before they figure out how to mine iron or copper or silicoln to make electric writing. Why make water grooves with dipoles (which wouldn't even work that well) when the grooves read just fine without water?
Sorry for the long post. Didn't anyone else here take physics and chemistry?