Thread Subject: Contour graph help!

I'm looking to make a contour graph with:
X-axis being dates (increasing to the right)
Y-axis being different lake water depth(increasing downward)
and Color from red to blue on the graph indicating various
temperatures with legend indicating which color is which
temperature.
This way you can find the temperature of the exact data and
water depth by comparing the color at that point with the
legend.
How do I do that in matlab? I tried contourf but couldn't
get it to work right. I'm using an old version of Matlab
right now (5.3), but if the method is for the newer
versions, it is welcome too, since I might be able to get my
hand on a newer copy.
Thanks