Fish finder or depth sounder for the shallows

[chewi]

They do radiate the cone outwards, I can't remember what the typical values are but, of course, in shallow water it's still not going to have much of an effect so won't be much more than straight down in reality.
It was only a few weeks back that I had to take a boat into a local boat club located right up in the saltings of the Medway, somewhere I'd never been before.
A large expanse of featureless water around 2' deep with a winding channel leading through it, very narrow but with around 5' of water in the gulley at high tide.
The chap I was with seemed very impressed at my ditch crawling prowess when we reached the club, but I have to admit that there was no skill involved, just (very slowly) following the channel on the plotter and tracking it on the fishfinder!
I've no doubt it would have been as straightforward with a depth sounder, but it was extremely helpful to be able to see the sides of the gulley coming up if we drifted slightly off course.
I have to point out that I'm new to boating in general, and a more experienced navigator would probably have had no qualms about finding their way in, but I found it invaluable to be able to see if a rapid change in depth was the gulley we were following or just an obstruction or a hole.

My Garmin has an alarm , and a second alarm via the plotter, so I don't take much notice until it wakes me up.
I use the first as a heads up at 2.0m in case I am distracted and dont realise I'm heading into shallows ( I draw 1.1m)
The second is at 1.2m, and I watch it like a hawk after that.

I've never used it for finding fish, they can stay where they belong!

 

[FairweatherDave]

..........
I use the first as a heads up at 2.0m in case I am distracted and dont realise I'm heading into shallows ( I draw 1.1m)
The second is at 1.2m, and I watch it like a hawk after that.

I've never used it for finding fish, they can stay where they belong!

Chewi, apologies for pushing you but are you talking depths or depths under the keel? I can see that 10cm would be cutting it more than fine. Presumably once virtually aground the fish finder can't really help much either.
And purely out of curiouslty are you a bilge or fin keel? I really enjoyed Poole harbour with a bilge keeler and was quite happy that going aground would not be the end of the world (even though the rising tide rose so slowly).

 

[chewi]

Chewi, apologies for pushing you but are you talking depths or depths under the keel? I can see that 10cm would be cutting it more than fine. Presumably once virtually aground the fish finder can't really help much either.
And purely out of curiouslty are you a bilge or fin keel? I really enjoyed Poole harbour with a bilge keeler and was quite happy that going aground would not be the end of the world (even though the rising tide rose so slowly).

I set the offset to show depth of water, not clearance from the bilge keels, (I find that way easier to work out the scope for anchoring) so yes the second alarm at 1.2 is very close for my 1.1 draft, but it works.
You do need to be at crawling speed by then, to react in time or to ground gently. I can reverse off a gentle grounding, but anything fierce on a falling tide and it's too late.

 

[Keith 66]

We have a fishfinder on our Sabre 27, the transducer is mounted fwd & it looks forward to some degree. It does the same job as an echo sounder but you see what the bottom is doing & how quick its shallowing. For ditch crawling in a boat drawing 4ft 8" its an absolute must! All for less than £100

 

[BrianH]

We have a fishfinder on our Sabre 27, the transducer is mounted fwd & it looks forward to some degree. It does the same job as an echo sounder but you see what the bottom is doing & how quick its shallowing. For ditch crawling in a boat drawing 4ft 8" its an absolute must! All for less than £100

It is this displayed trending attribute I too appreciate. No need to fix one's gaze on a varying digital number and mentally interpolate the result; one glance and the shoaling or deepening, together with its steepness, is immediately revealed. I am based in, and like to explore, a labyrinth of Italian lagoon channels that are not charted with any permanent accuracy, such is the tidal scouring. In such an environment, a fish-finder is invaluable. And, as you mention, a fraction of the price of a number-only display - or so it was when I queried replacing my own defective instrument.

 

[ex-Gladys]

It is this displayed trending attribute I too appreciate. No need to fix one's gaze on a varying digital number and mentally interpolate the result; one glance and the shoaling or deepening, together with its steepness, is immediately revealed. I am based in, and like to explore, a labyrinth of Italian lagoon channels that are not charted with any permanent accuracy, such is the tidal scouring. In such an environment, a fish-finder is invaluable. And, as you mention, a fraction of the price of a number-only display - or so it was when I queried replacing my own defective instrument.

One of the benefits of integration between kit.. I have the depth info going to my plotter ( I know the OP doesn't have one) and can display the depth profile at a tap or two of the screen.

 

[Keith 66]

There is a flip side, you need to be careful because it is all to easy to watch the depth & bottom trace & get caught out. Couple of years ago beating out of the medway in a NE f5 , boat crashing to windward, we tacked at the eastern side of the entrance & went of on port tack. Now anyone who has sailed here will know that the channel is 70 - 80ft deep & the western edge of the medway channel is very steep to. Well there i was watching the sails, waves & fishfinder, as we came up fast on the Grain spit it was reading nearly 80ft, all of a sudden the trace went damn near vertical & we threw a tack in instantly. As she came round it was reading zero & we were nearly ashore. As the boat paid of on the other tack & the water deepened I looked over my shoulder to see a couple of seagulls paddling in the shallows not much more than a boats length in front of where we had tacked. The moral of the story is look where you are going as well!

 

[ianfr]

Which fishfinder do you use?
I am thinking of replacing my Nasa depth sounder which loses the plot sometimes in shallow water. In the East coast that is a pain.

Do the Transom mount transducers work OK when used in hull?

Thanks

Ian

 

[chewi]

Which fishfinder do you use?
I am thinking of replacing my Nasa depth sounder which loses the plot sometimes in shallow water. In the East coast that is a pain.

Do the Transom mount transducers work OK when used in hull?

Thanks

Ian

My Garmin "transom mount transducer" certainly works in hull.
It said that on the tin .
I araldited it close to the c/line as far fwd as I could get it.
It has never given any failure in 10yrs+

 

[Murv]

Which fishfinder do you use?
I am thinking of replacing my Nasa depth sounder which loses the plot sometimes in shallow water. In the East coast that is a pain.

Do the Transom mount transducers work OK when used in hull?

Thanks

Ian

Personally, I use the Raymarine sonar/down vision dragonfly units. Official line is that they can't be used in the hull, but I've never had any problems when bedded down in CT1
Currently using the 4 pro purely because it can stream through wifi to a tablet. They also make a "black box" version that can only stream the image to a tablet or phone.