Thanks for the inquiry. Biller has made quality spearguns for a long time. Unless the gun has been subject to many years of use or been terribly neglected and allowed to corrode, then chances are good that the gun is very serviceable – once you add fresh bands etc. However, it is not the right tool for your application.
There is no agreed upon standard for the measurement of spearguns. For example, it is my understanding that a 32 Biller is a little longer than 32 inches from the rear of the butt pad to the front of the muzzle (the shaft will stick out several inches more). Their website indicates that total gun length is 35 inches
The Biller gun has a butt extension which extends rearward of the handle, probably 6 or 8 inches- would be my guess. This means that the band stretch distance (distance from the front of the gun to one of the shaft notches) is significantly less than 32 inches, maybe on the order of 22 inches. These are rough guesses.
So the 32 Biller has a rather small shaft (their website indicates the total shaft length is just 30 inches long) This means that the gun has a limited band stretch and therefore has a limited range. It is best used in limited visibility or for shooting under holes. The Biller gun is too short for 50 to 70 ft visibility. You could definitely use it, but you would be significantly hindered.
MAKO “pipe” guns and most euro guns use a different measuring convention. In general, we use metric (cm) and we ONLY consider the barrel length. So a 90 cm gun has a 90 cm (35.4 inch) barrel, the handle extends rearward and the muzzle extends a few inches or so forward, meaning that the total length of a 90 cm is a good bit longer than 90 cm. For example, the 90 cm has a total length of about 55 inches if we include the typical 11 inches of spear shaft overhang on the front end.
So to make a long story short, a 32 Biller gun is about 35 inches long and shoots a 30 inch shaft while a 90 cm MAKO gun is about 44 inches long and shoots a 130 cm (51-inch) shaft and has a band stretch of almost 90 cm (35 inch). I go through all these details because if you didn’t understand this you might think that Biller 32 (with a length of 35 in) is somewhat comparable in power and range of a 90 cm MAKO gun and they are not.
Most experienced hunters would probably choose a 110 cm (MAKO) gun for that kind of clear water. This is a pretty big gun and is a stretch for a shorter person to load easily. So I think a reasonable compromise for someone like yourself would be a 90 or 100 cm gun. As mentioned we can adjust the band length and size as needed.
In general, I would not recommend a roller muzzle gun for a scuba diver who is just starting to hunt with guns. The simplicity of the standard muzzle gun will be appreciated.