Construct a inexpensive hydrophone out of things laying around your house.
I decided to put up this instructable because (to my surprise) no one has a hydrophone instructable up yet. I made mine using a mixture of other people's hydrophone creations that I found through a google search and a bit of ingenuity.
Here's the parts that I used but it should be fairly easy to adapt whatever similar items that you can find.
knife or scissors
( I used a small spray bottle that was originally some "energy-caffeine spray")
Step 1: Breaking Down Parts
You are going to dissasemble the computer mic so that you have the capsule and the cord seperated, I didnt put any pictures of this up because I already disassembled them before deciding to make an instructable, but the proccess is pretty easy and is a little different with every mic.
You also should have your bottle or container taken apart.
Step 2: Cut, Strip and Connect
Using a small pear knife make a hole in the top of the lid and feed the cord through. It is important to make the hole as small as you can so it as water tight as possible.
After the cord was in I stripped the wires and connected them to the Mic Capsule by carefully twisting the wires together.
Step 3: First Test
It is a good Idea to test the connection before soldering and wrapping everything.
Plug the mic into your computer or recording device and test it.
Step 4: Soldering and Wrapping Connections
If your test was successful then you can solder your connections.
If it was not make sure that your wires are in the right spot and that they are well connected also check the volumes of your recording equiptment.
There are a lot of different ways that you can do this, but you need to insulate the wires so that they do not touch each other, the mic capsule, or water.
If I had access to a glue gun I would of sealed them that way instead I used plastic wrap, and indiviually wrapped the connections and then wrapped them all together.
After you do this its a good idea to test the mic one more time.
Step 5: Fitting the Capsule
Now you should continue to wrap the capsule with plastic wrap until the capsule fits tightly in the lid, but not so tight that you can't fit the lid over the opening of the bottle this may take some trial and error.
Step 6: Vegitable Oil
Pour vegetable oil into the bottle until it is nearly at the top, leaving a little room for the mic capsule.
Push the lid over the bottle opening, the mic will dip into the vegetable oil and go into the bottle,
The lid should stretch and go over the bottle and create a near air-tight seal, some vegetable oil will probably come out be sure to wipe off the oil before putting it in water, you do not want any air in the bottle it should be full of oil.
I taped around the edge, where the lid was over the bottle and wrapped more plastic wrap around it to make sure it was sealed well.
It is also a good idea to seal the lid where the cord is at with hot glue or super glue.
Step 7: Done
Now you can test out your hydropne, its not exactly research quality or anything but it does work, you will also want to make some sort of weight to hold it under water as it does want to float.
A key ring with some old keys works great.