Ultrasonic water level meter

Hi,

Basically I'm trying to make a water level meter using some ultrasonic transducers, however I have no idea how to use them or what I need to get to use them?

I've got access to the following: http://www.jaycar.com.au/products_uploaded/AU5550.pdf

I understand I need something to give it a 40 KHz pulse with width 0.4 ms, but I don't think the arduino can do that alone?

If anyone could help me it would be much appreciated!

You could go with an already built sensor, giving analogue output.

Look for robotic sensors like here : http://www.maxbotix.com/

It costs around 25 euros, but for a 24/7 operation I would avoid it and go with a simple simple solution, float switches.