fisheye versus wide angle lens

I have a canon wpdc30 housing for my a75 digital,and am looking to get a wide angle lens for it.What is the difference in wide angle versus fisheye and which would be the better all around lens for someone on a tight budget?

A wide angle lens had just that: a wide angle of view. Conversion lenses for consumer digicams will typically give you somewhere in the region of 100º to 120º, depending on your camera and the lens you use.

A fisheye lens will give you a 180º view, which results in a rather distorted image, but this is generally not a problem when underwater, and yields very attractive images. Only thing is you need to get REALLY close to your subject, and you have to be careful not to have a fin or a hand in the picture.

I personally prefer fisheye lenses underwater, but for an "all-round lens", the WA lens is probably more adequate, as it allows you to shoot medium sized subjects from very close, or larger subjects from a bit further.

The classic difference between the two lenses is that the WA lens is rectilinear, which means that straight lines come out straight in the image. The FE lens is not. Straight lines end up curving unless they go straight through the center of the image. On land, where there are lots of straight lines (horizon, buildings, rooms, doors, furniture, etc.), the FE images look very distorted. Since there are not a lot of straight lines underwater, you tend not to notice so much, and the extended field of view can be very dramatic. Another problem with the FE is that since it has a much wider field of view, you can often get sun flare, a stray cable, or a flipper in the image.

As an all around lens, I recommend you get the WA since it has fewer issues. Of course many consider these issues as opportunties.

Just a note to what already said here before: also with the WA non fish-eye lens you'll get some distorted image, at list with the Inon AD105 that I have(and gives an angle of ~105 degrees) I have some distortion, its not disturbing u/w as its already said but its there but of course not close to the distortion of my 10.5 fish-eye lens.