I've posted on this subject several times before, but will try to summarize here.
We have had an Interphase Probe on both Insatiables, starting in 1996. We spend lots of time in poorly charted areas, some of which do not enjoy clear water. We explore anchorages
new to us frequently.
1. The display does require some experience to interpret usefully... just like a radar
display does. It isn't rocket science, and a few hours of paying attention to the forward picture in known waters will sort out most issues.
2. The useful forward range is a function of the depth
. Under most conditions one gets a useful view of the bottom at somewhere between 3 and 5 times the depth
. Note that this is looking at the bottom. In deeper water one can see things like a bommie sticking up from the bottom much further ahead. We have seen coral
reef walls from around 800 feet distance, for instance, in a lagoon
that was on the order of 50 feet deep.
3. Surface waves make "noise" that hides things like floating objects that do not protrude deeply into the water, things like logs
or in rough conditions, even a container (no data, just a guess).
4. The alarm
system is useless IMO. If you set the gain low enough to avoid frequent false alarms the detection range approaches zero. This means that one needs to watch the display for it to be useful. Note: ours are older models. They may have improved the alarm
algorithms in later editions.
5. Our bottom line is that we find them useful and in fact essential for our sort of cruising and our degree of cowardice in strange waters. They are perhaps not as good as shown in the glossy brochures, but they are sure as hell better than nothing.
As for using a fish finder pointed forward: a waste of time and money
HOpe that this has been helpful. A bit of searching should find some earlier and more detailed posts on the Probe.