Jeffrey's response (it being basically the opposite of what you were told) is a good indicator that one size doesn't fit all, so to speak. You were told low iso because the higher the iso the grainier the picture, so to get the finest quality you'd want the lowest iso. But... using a low iso means your shutter speeds are going to be slower, which in turn means that anything that's moving in the picture (swimming fish, polyps swaying in the current, etc.) will end up blurry-- hence Jeffrey's advice.
Same concept for the aperture in terms of how it affects the shutter speed- the higher the fstop number the slower the shutter speed. But you were told to use a high fstop because the higher the fstop the greater the depth of field... depth of field, by the way, is described as the amount of the image that appears in sharp focus.
So you can see from all that (hopefully not too confusing
) that there is no set of ideal settings- you have to determine what is most important (for each picture you take)- depth of field or a fast enough shutter speed to stop the movement. And this... is the heart of photography... so once you've understood how each setting affects the others you are a master photographer
I see that the W7 doesn't have aperture or shutter priority but it does have full manual exposure mode-- that's where you set both the aperture and the shutter speed youself. If you want to really control the results try manual mode. I suggest experimenting with very small apertures (high fstop number, like f10 when you're zoomed all the way in or f5.2 at full wide angle) to see what a lot of depth of field looks like. Be warned though- the shutter speeds are going to be slow, so anything moving will be blurry. You will have to experiment with different shutter speeds to get the proper brightness [exposure]. If the picture turns out too dark choose a slower shutter speed, too bright means you need a faster shutter speed. As a very rough starting point you could try f5.2 and a shutter speed of 1/60, with the camera 6cm from your subject.
With the lens at full wide angle you can have the camera as close as 6cm to your subject. I couldn't find a specific distance for when you're zoomed all the way in, but it's probably around 9 or 10cm. You'll have to experiment and see what works for you.
Post some pics and we should be able to make some recommendations on how to improve them.
Greg
