Introduction
I love LED graffiti, but I don't like the idea that the batteries die after a short time, after which point it becomes just more junk.

Solar garden lights (normally used to adorn a path) are simple devices which use solar panels to charge a rechargeable battery in the day, then they automatically switch an LED on at night. Since they are now very cheap, and are even often thrown away, so we can use these to create self-sufficient (EVER LIVING!) glowing graffiti to adorn your garden or neighbourhood.

After thinking about places for an installation - somewhere interesting, beautiful, that wouldn't get disturbed - I decided on underwater.

So, inspired by nature, this art project re-creates beautiful, mysterious, bio-luminescent creatures from the deep sea in your urban canal, pond or river environment. In the initial test phase of this project, I built 2 creatures, one based loosely on a jellyfish and the other on a sea slug.

Method
Essentially we take some cheap solar LED garden lights and re-hack them into creatures shapes, using mostly hot glue. The solar panels float on the surface of the water like lily pads and the LED creatures are submerged a few inches below the surface so that their glow is visible from the bank, pondside, or canal towpath.

You will need
+ solar LED garden lights - any type can be made into creatures, use you imagination! I used one fibre optic 'brush' type, and another basic light set
http://www.maplin.co.uk/10-piece-fibre-optic-solar-light-set-508447
http://www.thesolarcentre.co.uk/products/Solar_Garden_Lights_10_Pack-75-7.html
+ (optional) flashing LEDs or flashing LED toys, e.g. LED rope necklace
http://shop.noveltyimports.co.uk/led-chase-rope-necklace-569-p.asp
http://alan-parekh.vstore.ca/flashing-5000mcd-p-88.html
+ soldering tools and very basic electronics
+ a lot of hot glue for sticking and waterproofing
+ small containers which can be made waterproof using hot glue
+ sand maybe as ballast

OK let's go!

Step 1: Creature 1: Sea Slug

This is an easy project, using a fibre optic brush-type garden light. This type of garden light consists of a control box, containing a solar panel, battery, switch and circuits. This control box has power leads which are connected to all 10 brush LED lights in parallel. We won't need to modify any electronics in this one, just re-solder the wires on the LEDs.

STEPS
1. cut all the brush lights free
2. use hot glue to stick the brushes to a 'body'. I used cable ties glued together as a skeleton body as it's a bit flexible, and the same colour. You could use anything. For example, if you were making a sea anemone, you might use an upside down plastic bowl, with the brushes sticking out radially. Enjoy creating whatever creature or non-creature shape you like!
3. re-solder all the LED wires in parallel. I used a breadboard here as you can see in the photo.
4. solder the power leads back on to the breadboard.
5. waterproof everything using liberal amounts of hot glue. CAUTION: use a lot of glue, but be careful - the glue melts the brushes, and if you get a blob of glue on the brushes, you face a sticky mess that is very hard to get out of!

6. that's it! arrange the device so that the solar panel floats on top, and the creature floats about 1-2ft below the surface, depending on how dark/murky it is!

I wish I had a video, the brushes sway underwater and look simply eerie and beautiful.

Step 2: Creature 2: Jellyfish (sort Of)

This is a more complex project which requires some basic electronic circuit building (a transistor, diode and resistor).
We take 3 of the standard type of lantern garden lights to bits, and use only the AAA rechargeable batteries and the solar panels.

outer ring is comprised of a flashing LED rope necklace.
inner glowing guts are 4 rings of clear plastic (cut from a deodorant lid) glued to a flashing RGB LED
solar panels are 3 x panels connected in series, glued in a they have polystyrene stuck on the underside to make them float
circuit is the following (link ), from here http://www.evilmadscientist.com/article.php/solar with 3x panels and 3 x AAA batteries
battery case is an old plastic tub, filled with sand to weight it.

Since this is an artistic project, you will probably not want to do it exactly the same as me. So I will talk about the technology and techniques rather than step instructions.

Why are we using 3 solar circuits?
I wanted to use some flashing / color changing LEDs, as they look fantastic. These need a steady 3ish volts to run off. Most cheap solar lights are 1.2v (1 panel and 1 AA or AAA battery). There are circuits (joule thief) that can step this voltage up to 3-4V, but they don't provide a steady voltage, it's a series of high pulses. So these can run a steady high-brightness LED fine, but they won't work with a flashing RGB, or flashing rope light - they will glitch out or just not flash.

what do I make it out of?
Look for any flashing LED toys, the type they give to kids at firework shows, or for people at electronic music events, and have fun!
make body shapes out of pieces of translucent plastic (most likely plastic lids or plastic bottles), glued to LEDs.

Step 3: Notes, Conclusions, Next Steps

Notes:
Both creatures looked amazing in the water at night, much better than I thought they would.

I am going to remodel the jellyfish slightly so that it floats about 1ft below the surface. The deeper they are, the more mysterious they look.

The light they emit is surprisingly very bright; also, the way they bob and float is fantastic, they would be even better in a river with current.

Multiple creatures would be even better, I am working on an installation of these for a festival at the end of July.

This was a fun project to work on, as you are building it in the light, it looks like a load of plastic rubbish, but then it totally comes alive in the water at night. The water diffuses the light slightly and gives it an eerie feeling.

There are a lot of other solar LED projects graffiti projects I'd like to get working on so watch this space.