Start by collecting the following items:

Tools
- hot glue gun and multiple glue sticks
- a hobby knife (aka exacto knife)

Materials
- one working electric remote control car
- two lego propellers*
- enough batteries for remote and car
- a sturdy** plastic bottle big enough to fit circuit board and batteris but not bigger
- the bottle's cap
- two or three corks
- electric tape
- duct tape
- a hand full of nails
- two or three feet of wire (I used wire from an old lamp but a smaller gauge (diameter) wire would probably work fine)
- WD-40 and/or automotive grease
- a plastic easter egg (optional)

Once you have collected your supplies you move on to step 1 and begin to take apart your RC car to 'harvest' the parts needed for your sub. You should know that your RC car will most likely be unrepairable after these changes.

*The best are the ones meant for lego boats or subs, though, some lego airplane propellers work... as you see in my own sub. See step 6 for a picture of these lego boat/sub propellers. You can can also buy fancy expensive propellers at any hobby shop.

**The plastic bottle must be sturdy because of the pressure that will be on it when diving deep. The deeper the dive the more the pressure. If your bottle crushes you run the risk of it leaking and damaging circuitry. It could also loose its buoyancy due to a change in volume causing it to sink out of the range of your remote. Unless you have a fishing line attached when this happens you could loose your sub.

Here is a video of the finished product at play:

(We attached a string to it while test driving just to be safe.)

Step 1: RC Car Organ Donation

Step 2: Submarine Hull From a Bottle

Step 3: Power Wire Modifications

Step 4: Sealing the Hull

Step 5: Finish the Hull

Step 6: Propulsion Systems

Step 7: Attaching Struts

Step 8: Connecting Propulsion Systems to the Hull

Just leave the motors open because the mechanics and electrical physics of the motors are not hampered by exposure to fresh water. Try to dry them out after a dive so as to avoid rust as long as possible. I would also avoid saltwater as it contains more ionized particles which could corrode the parts faster.

Step 9: Dive Fins

NOTE: I used plastic taken from the plastic body of the RC car to make these fins and it work very well. However, you can use any sturdy plastic to make these.

Step 10: Buoyancy in the Back

Step 11: Level and Nearly-Neutral Buoyancy

Step 12: Finishing Touches

At this stage you may want to add a little grease and WD-40 to your motors to help protect them form water damage.

Step 13: How to Dive

Enjoy your new RC Submarine!

Step 14: Additional Dive Designs: 2 Channel "Corkscrew"

An easy alternative to the original dive method is to angle the steering motor so that spinning in circles creates a corkscrew effect allowing the user to control depth more precisely, though in a less traditional style.

I have built and tested this design with great results.

Step 15: Additional Dive Designs: 3 Channel "3D"

If you can find (or buy) a three channel remote with motors than this is the design for you. The only change to the original design is an added channel and motor to control the up and down orientation.

I have yet to build and test this design.

Step 16: Additional Dive Designs: 4 Channel "Catamaran"

I plan to try this 4 channel version as my next project. The concept is simply to build a catamaran style sub with each pontoon based on the original design described on this instructable. The major difference being that the steering motors are used to control depth and up/down orientation.

One VERY IMPORTANT note is that if you plan to uses two remote control cars to make this version it is necessary that the cars be identical in every mechanical and electrical way except that they must operate on different channels. There are a number of car combo deals out there that sell two cars of the same type but with different channels so that users can race them. This would be ideal.

I have yet to build and test this design.