i bought a mako magnet last year...I'm not sure if it worked, but let me tell you my results...In two days of fishing I caught the following species of sharks: hammerhead, thresher, mako, and blueshark. Could have been a coincidence, but i will be using it from now on.
I have had em out and to be honest I can't say they work or not. They don't scare fish but can't say that they draw makos as such. The only sharks I have had take a pass at them are blue sharks and they aren't very picky. Actually had more interest from them trying to eat my transducers than the magnets...
i bought a mako magnet a few years back and used it on all trips and caught sharks on all trips. but also we had loads of chum and chunks in the slick. we did lose the magent to and interested shark while at the tea cup. we had it in a 5 gal bucket with the top on over the side of the boat. we heard some noise and when we pulled on the rope the magnet was gone including the bucket leaving just the rope and the electrical wire.
have not replaced it and we are still cathcing the old fashion way with lots of chum.
From what I'm hearing it seems like they are a waste of money, we really dont shark all that much...I dont believe there are too many big mako's left anyhow..and I dont really like playing with bunker chum all that much anyway