Fishfinder - to reef or not to reef

I have a Humminbird 386ci and I have trouble determining if I'm over a reef or not. Especially in Capitola. In Santa Cruz, it's a little easier. I see jagged red rock formations. For Capitola, most of the bottom looks red and yellow. Other than the gps coords on the map given by Capitola Boat Rental, how do you know if you are over a reef? Do I need a better fishfinder or is this a lack of experience user problem?

Do you happen to remember how many decimals there are in your GPS coordinates for those reefs ? Perhaps intentionally, many of the coordinates that I seem to come across online are missing the last decimal in the standard GPS format. Example: missing the Y decimal in XX XX.XXY coordinate. Meaning that it'll put you in the general area, but by no means are you on top of the exact spot so you may have to do some hunting. Then again, some of these reefs are large structures, or a series of structures that cover a decent footprint on th ocean floor. Often, the coordinates may put you in the middle of the reef but maybe not directly over the best, most distinct structure on the reef.

Not being able to see your screen, its hard to say. But if you're in the ballpark of your GPS coordinates for a reef and youre seeing jagged returns or sharp changesin depth, chances are that you'rd right where you want to be. Maybe hook up with someone on here who knows the reefs in question and tag along with them on a trip.

Not sure if any of that info helped ?

When I'm over a good reef the outline of the bottom looks like the EKG of someone with ventricular tachycardia.
Stop, drop the hammer and BAM!, get in the boat ling ling.

I use a Lawrence Elite 5 HDI chirp.

Do you happen to remember how many decimals there are in your GPS coordinates for those reefs ? Perhaps intentionally, many of the coordinates that I seem to come across online are missing the last decimal in the standard GPS format. Example: missing the Y decimal in XX XX.XXY coordinate. Meaning that it'll put you in the general area, but by no means are you on top of the exact spot so you may have to do some hunting. Then again, some of these reefs are large structures, or a series of structures that cover a decent footprint on th ocean floor. Often, the coordinates may put you in the middle of the reef but maybe not directly over the best, most distinct structure on the reef.

Not being able to see your screen, its hard to say. But if you're in the ballpark of your GPS coordinates for a reef and youre seeing jagged returns or sharp changesin depth, chances are that you'rd right where you want to be. Maybe hook up with someone on here who knows the reefs in question and tag along with them on a trip.

Not sure if any of that info helped ?

The gps coords for Boomer Reef is 36-56-355 121-57-737 and is as you said the general area. When I get there, I just drift. I cannot tell if I'm on or off the reef. Thanks, this helps. I will hook up with folks that know the reefs and then I will know what a reef looks like on my fishfinder.

When I'm over a good reef the outline of the bottom looks like the EKG of someone with ventricular tachycardia.
Stop, drop the hammer and BAM!, get in the boat ling ling.

I use a Lawrence Elite 5 HDI chirp.

Ghan, do you use the zoom feature to view the bottom and do you use 200khz or 83khz? At 80 fow, the bottom on my screen looks bumpy and it's like that most of the time with the exception of a few bigger bumps. Nothing like what you are describing.

Google Earth actually has a little bit of cursory bathymetic data for shallower depths. If you put that coordinate into Google Earth and zoom way in, you can get an idea of what the sea floor looks like in that area. It looks like there's a long depression that runs from southwest to northeast through the reef area.

Google Earth actually has a little bit of cursory bathymetic data for shallower depths. If you put that coordinate into Google Earth and zoom way in, you can get an idea of what the sea floor looks like in that area. It looks like there's a long depression that runs from southwest to northeast through the reef area.

Chattich, I had to google bathymetric. Thanks, learned a new word. Always wondered about Google earth and how accurate it was. it shows contours for some reefs and not others. I will check all my gps coords against Google Earth. This definitely helps me pick out some spots to try out instead of just wondering aimlessly around. Thanks again!

remember depending on the sea condition.
as you ride up and down the chop, a flat bottom can look jagged
also im looking more for a good solid yellow line

remember depending on the sea condition.
as you ride up and down the chop, a flat bottom can look jagged
also im looking more for a good solid yellow line

john, yellow line? for my fishfinder, red indicate hard rock and yellow for something softer. So I usually see a red line on top of yellow. Am I misinterpreting my fishfinder?

remember depending on the sea condition.
as you ride up and down the chop, a flat bottom can look jagged
also im looking more for a good solid yellow line

john, yellow line? for my fishfinder, red indicate hard rock and yellow for something softer. So I usually see a red line on top of yellow. Am I misinterpreting my fishfinder?

your right on the money

Ghan, do you use the zoom feature to view the bottom and do you use 200khz or 83khz? At 80 fow, the bottom on my screen looks bumpy and it's like that most of the time with the exception of a few bigger bumps. Nothing like what you are describing.

I use the 200khz - narrow cone.  The yak is not moving, why do you need the wide cone 83khz?
I don't use the zoom feature.

remember depending on the sea condition.
as you ride up and down the chop, a flat bottom can look jagged
also im looking more for a good solid yellow line

I thought riding the swell would only affect depth read out, I'm not sure how that changes the way the bottom, or anything between you and the bottom looks.

remember depending on the sea condition.
as you ride up and down the chop, a flat bottom can look jagged
also im looking more for a good solid yellow line

I thought riding the swell would only affect depth read out, I'm not sure how that changes the way the bottom, or anything between you and the bottom looks.

im really unsure now, i wonder if ping speed would change that.

Ping speed was my other thought as well. The faster the ping speed, the more gradual the bottom features will look. And it really depends on the reef itself as well - no two are the same. Some reefs are just more subtle/less jagged to begin with.

Also, check out the Navionics web app as well ... http://webapp.navionics.com/?lang=en Make sure to click on the "user sonar" icon in the lower left of the screen to get more detailed info.

Ghan, do you use the zoom feature to view the bottom and do you use 200khz or 83khz? At 80 fow, the bottom on my screen looks bumpy and it's like that most of the time with the exception of a few bigger bumps. Nothing like what you are describing.

I use the 200khz - narrow cone.  The yak is not moving, why do you need the wide cone 83khz?
I don't use the zoom feature.

Good point. I have been using 83khz and unless I zoom in, bottom look like rolling hills. I will try 200khz the next time out.