Fish finder or depth sounder for the shallows

[FairweatherDave]

I don't use a plotter and I'm toying with replacing the depth sounder (which needs replacing) with another depth sounder or a fish finder. I like the simplicity of a depth sounder but as someone who likes thin water sailing in my bilge keeler should I go for a fish finder? Cost and power consumption seem comparable but I am worried about the information overload of a fish finder. In Poole I went aground and suspect a fish finder would have helped keep me in the channel. I have no intention of fishing but is the information from a fish finder easy to use and not too distracting?
Can a cheap one be easy to read in bright sunlight? Thanks for any experienced thoughts. (All the threads I find on this seem quite old)

 

[NormanS]

My Fishfinder is part of my Plotter, and I find it invaluable for finding clear ground for anchoring, but as well as showing that, there is also a clear digital display of the depth. I would imagine, but don't know for sure, that most fish finders will show the depth in numbers.

 

[prv]

I've not used a real fishfinder in anger, but my understanding is that they still only look downwards and so show what you've just passed over. I can't see very much use in that over what you get from a depth sounder. Ideally what you want for nosing around in shallow water is a forward-looking sonar:

...but the prices put them out of reach of most of us.

(That's an actual screenshot from EchoPilot's top-of-the-range instrument.)

Pete

 

[BrianH]

I've not used a real fishfinder in anger, but my understanding is that they still only look downwards and so show what you've just passed over. I can't see very much use in that over what you get from a depth sounder. Ideally what you want for nosing around in shallow water is a forward-looking sonar:
...but the prices put them out of reach of most of us.

But doesn't the common-or-garden, affordable depth sounder also just look down? Mine did.

My fish-finder, which I replaced my VDO depth sounder with, has a large screen with numerical depth display in nice big numbers at the top and a graphic display of the bottom against a scale that varies on the vertical axis. The benefit is that the nature of the bottom shows - mud, sand, rock, etc, by indicating with the hardness of the line. Not only a better representation than the old number only, but much, much cheaper for unit price. The only downside is it needs more mounting space and is not suitable for console flush fitting. I have plenty of wheelhouse, chart-table real estate so it fits well.

 

[FairweatherDave]

I can see that anchoring in unfamiliar places would be helped by a fish finder where you can check out the bottom. Obviously forward facing info would be great for skimming over the mud but that is beyond my budget and ambition. I suppose I am asking if any shallow water sailors (who like gambling as they cross the green bits) eg of Poole or Chichester like fish finders or do they stick with what they have coz it hasn't bust, and maybe study their plotters instead. The point about more mounting space is one good reason why I am likely to stick with replacing like for like. When I went aground my depth sounder was showing 1.3 under the keel which might have been its last clear reading before going over a soft patch, and I know I made other mistakes that are simply dumb (in retrospect). But would a downward pointing fish finder have really helped in this circumstance? I quite like just watching the number read out go up or down but I have read some posts very firmly saying you are crazy not to get a fish finder come replacement time.

 

[prv]

But doesn't the common-or-garden, affordable depth sounder also just look down? Mine did.

Exactly. So apart from the possible stuff about bottom composition, which I can't say has ever particularly interested me, a fish finder doesn't seem to do any more for the typical yachtsman than the more normal depth-sounder.

Pete

 

[prv]

When I went aground my depth sounder was showing 1.3 under the keel which might have been its last clear reading before going over a soft patch

My ordinary sounder gets a good solid "0" reading off mud that I can push my keel through, so I wouldn't have thought the problem was deep mud absorbing the echoes. If that 1.3 was in metres below the keel, and you grounded on a sand or mud bottom (ie no sudden rock pinnacles to miss and then catch the keel on), then that's obviously pretty worrying, but possibly a fault with the instrument itself - or maybe double-bouncing? I've heard of that though not knowingly seen it in practice.

Pete

 

[pagoda]

My ordinary sounder gets a good solid "0" reading off mud that I can push my keel through, so I wouldn't have thought the problem was deep mud absorbing the echoes. If that 1.3 was in metres below the keel, and you grounded on a sand or mud bottom (ie no sudden rock pinnacles to miss and then catch the keel on), then that's obviously pretty worrying, but possibly a fault with the instrument itself - or maybe double-bouncing? I've heard of that though not knowingly seen it in practice.

Pete

The easy solution is creep ahead, with somebody at the bow handy with a lead (and wax insert). That way you have some idea of the bottom and get audible / visual feedback from the bow as you progress. Don't trust electronics too much?

 

[FairweatherDave]

Like I said I made a stupid mistake. I do think my depth sounder is temperamental from other experiences and the display fades in and out at the start of the season but my mistake this time was inexperience and stupidity! I was sailing in a narrow shallow channel inside Poole harbour in grey rainy gusty conditions, watching the depth sounder and the Navionics on the tablet (a new experience) and did not spot a channel marker in the real world. I thought I could cut a wee corner as the depth guage indicated I was okay.......
Had I been motoring gently I doubt I would have gone aground as so much less would have been going on ( I was really enjoying my shallow water sailing........... inexperience....... basically driving too fast for the road with my lack of knowledge of that area)

 

[pagoda]

Like I said I made a stupid mistake. I do think my depth sounder is temperamental from other experiences and the display fades in and out at the start of the season but my mistake this time was inexperience and stupidity! I was sailing in a narrow shallow channel inside Poole harbour in grey rainy gusty conditions, watching the depth sounder and the Navionics on the tablet (a new experience) and did not spot a channel marker in the real world. I thought I could cut a wee corner as the depth guage indicated I was okay.......
Had I been motoring gently I doubt I would have gone aground as so much less would have been going on ( I was really enjoying my shallow water sailing........... inexperience....... basically driving too fast for the road with my lack of knowledge of that area)

Good quote.
Use electronics as a guide where "not to go " , rather than the opposite? If I am somewhere a little dubious , I will always slow down, always trickle along the middle of the suggested deepest channel, have someone at the bow on watch? (don't be tempted by how close can I go?)
Not foolproof, but on average workable.

 

[chewi]

The fishfinder shows a time graph of the bottom as you proceed, so If approaching shallows you can see the rate of rise much more readily than mentally plotting a graph from a depth sounder. If passing over a shallows you can see whether it is still rising when you get towards the depth you're prepared to go to.
Go for a fishfinder, no question.

edit .. particularly eg in Poole!
My mooring is south of the N channel, so I have to cross middle sands to get fuel/water etc from Salterns or go the long way round. As I pass over the shallows I can see the gradient level out as I get approach keel depth, but if its still rising fast I can see I will not make it.

 

[mainsail1]

Bought a Garmin fish finder early in the season for a small boat that I have on a trailer. The fish finder came with a full set of electronic charts for UK and northern France and is a great little plotter. For just over £200 it is excellent and shows the depth and bottom in considerable detail. Would I put one on my larger sailing boat which has a separate plotter and depth readout? Probably will if the present set up gets old or faulty.

 

[Murv]

First off, I'm a moboer so different requirements but the principle is the same.
I have a budget fishfinder with the transducer mounted in a forward part of the boat. Absolutely invaluable when creeping around in shallow water and has saved my props on several occasions.
Also fantastic for following channels across mudflats, it's far easier to be able to see the channel on the screen than try to keep track of the numbers rising and falling (for me, anyway.)

 

[BrianH]

Exactly. So apart from the possible stuff about bottom composition, which I can't say has ever particularly interested me, a fish finder doesn't seem to do any more for the typical yachtsman than the more normal depth-sounder.

Pete

You never anchor?

 

[prv]

You never anchor?

I anchor a great deal, but unless the bottom is sheet rock (which doesn't exist in my home sailing area, is uncommon anywhere else I've sailed, and isn't generally found in places you'd want to anchor anyway) I just drop my nice big Spade and it digs in.

Pete

 

[FairweatherDave]

I have a budget fishfinder with the transducer mounted in a forward part of the boat........
...... fantastic for following channels across mudflats, it's far easier to be able to see the channel on the screen than try to keep track of the numbers rising and falling (for me, anyway.)

Thanks Murv, that's exactly what the stuff I have read about claims. And from your description although in the front of the boat the transducer is facing directly down. Likewise thanks Chewi for the Poole related comments and Mainsail. Still interested to hear if other ditch crawling bilgies and the like have positive experiences with fish finders. Part of me still sees them as a bit of a hypnotic high tech toy drawing my eyes away from my surroundings above water level, but I guess you only need to look at it when you want that info. I know they have a digital read out too like a trad depth sounder.

 

[Murv]

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.

 

[pathfinderstu]

I anchor a great deal, but unless the bottom is sheet rock (which doesn't exist in my home sailing area, is uncommon anywhere else I've sailed, and isn't generally found in places you'd want to anchor anyway) I just drop my nice big Spade and it digs in.

Pete

 

[pathfinderstu]

If the bottom is fouled with debris or scattered rocks etc its quite easy to get a hitch round them when swinging at anchor that only a diver can undo, talking from experience here..haha, a fish finder will pick these things up.

 

[prv]

If the bottom is fouled with debris or scattered rocks etc its quite easy to get a hitch round them when swinging at anchor that only a diver can undo, talking from experience here..haha, a fish finder will pick these things up.

Fair point, that's a tick in favour of good fishfinders although not quite what I meant by "bottom composition".

Still doesn't make me want to rush out and buy one though

Pete