I have used the circle search technique allot, mainly looking for things people dropped off the boat.
The biggest thing that I found was that you need a secure center point so that you can keep the line tight, something you can't drag out of position. Also, swim slowly so that the drag of the line doesn't pull you off your pattern.
If I'm looking for something small I overlap my circles by no more than 1.5x the visibility that way I have some overlap of coverage of previously searched area. Sometimes I only go out 1 visibility length and only look one direction instead of looking right and left. If i think that what I'm looking for might stick up a couple feet off the bottom, and the bottom is pretty flat, then Ill start with a large circle and keep the line tight and drag it on or close to the bottom as I can to try and hang up on the target. If I don't find what I'm looking for I start decreasing my circles and search visually. It's amazing how fast something big can get buried.
As for line, I have used orange cave line in the past and it has worked pretty well. Thinner line is better due to less drag in the water so I'm trying 300lb test, orange, braided fishing line now. It can be a pain because it is so thin it can tangle pretty easy compared to cave line but it has WAY less drag in the water.
For the size area you're searching don't try and do it all in one search. Break the area up into multiple smaller circles. The largest circle I have ever been able to do with relative accuracy had a max radius of about 90'. It required swimming slowwww and keeping the line tight and was quite a bit of work because it's almost a 200 yard swim for each pass when you get to a 90' radius. The search was on a flat sandy bottom with very little current and it was done on multiple dives, staking the reel in place at the last point between dives. I might be able to extend that 90' with the braided fishing line I have now but I don't think I'll try it because that is already huge area covered in a search. Smaller search areas go faster, are easier to do, and if you plan your search on the known info you can narrow down a huge area to the best spots pretty quickly.
If you're searching for something someone lost off a boat, ask if they have any pictures that where taken while they were on the boat about the time they lost the item. If there is a background in the pictures, look for lineups in two directions. Look for a telephone pole or a tree and how it lines up with another landmark. Look at buildings and see if they just touch in the picture and then try and recreate those sight lines and drop your anchor there. It will get you close.
Or ask if they got GPS numbers where they were anchored when they dropped whatever it was you're searching for.
If you want to have fun and practice circles with a possibility of finding something cool, go to a popular anchorage after a big holiday weekend and do random circle searches. You'd be amazed what you can find. You can also pick up allot of trash, do your good deed, and fill your karma bank.
One other thing, take multiple, sharp, line cutters. With that much line out, especially in low viz, you could find yourself in a mess if you're not careful. I normally have a trilobite on my right shoulder, a DGX cutter in a bungee mount on my left forearm, and a pair of safety shears in a pocket on my thigh. You can always add a BFK for fighting off sharks.
Good luck in your search.
The biggest thing that I found was that you need a secure center point so that you can keep the line tight, something you can't drag out of position. Also, swim slowly so that the drag of the line doesn't pull you off your pattern.
If I'm looking for something small I overlap my circles by no more than 1.5x the visibility that way I have some overlap of coverage of previously searched area. Sometimes I only go out 1 visibility length and only look one direction instead of looking right and left. If i think that what I'm looking for might stick up a couple feet off the bottom, and the bottom is pretty flat, then Ill start with a large circle and keep the line tight and drag it on or close to the bottom as I can to try and hang up on the target. If I don't find what I'm looking for I start decreasing my circles and search visually. It's amazing how fast something big can get buried.
As for line, I have used orange cave line in the past and it has worked pretty well. Thinner line is better due to less drag in the water so I'm trying 300lb test, orange, braided fishing line now. It can be a pain because it is so thin it can tangle pretty easy compared to cave line but it has WAY less drag in the water.
For the size area you're searching don't try and do it all in one search. Break the area up into multiple smaller circles. The largest circle I have ever been able to do with relative accuracy had a max radius of about 90'. It required swimming slowwww and keeping the line tight and was quite a bit of work because it's almost a 200 yard swim for each pass when you get to a 90' radius. The search was on a flat sandy bottom with very little current and it was done on multiple dives, staking the reel in place at the last point between dives. I might be able to extend that 90' with the braided fishing line I have now but I don't think I'll try it because that is already huge area covered in a search. Smaller search areas go faster, are easier to do, and if you plan your search on the known info you can narrow down a huge area to the best spots pretty quickly.
If you're searching for something someone lost off a boat, ask if they have any pictures that where taken while they were on the boat about the time they lost the item. If there is a background in the pictures, look for lineups in two directions. Look for a telephone pole or a tree and how it lines up with another landmark. Look at buildings and see if they just touch in the picture and then try and recreate those sight lines and drop your anchor there. It will get you close.
Or ask if they got GPS numbers where they were anchored when they dropped whatever it was you're searching for.
If you want to have fun and practice circles with a possibility of finding something cool, go to a popular anchorage after a big holiday weekend and do random circle searches. You'd be amazed what you can find. You can also pick up allot of trash, do your good deed, and fill your karma bank.
One other thing, take multiple, sharp, line cutters. With that much line out, especially in low viz, you could find yourself in a mess if you're not careful. I normally have a trilobite on my right shoulder, a DGX cutter in a bungee mount on my left forearm, and a pair of safety shears in a pocket on my thigh. You can always add a BFK for fighting off sharks.
Good luck in your search.
