Lead is kinda on the outs as far as a fishing weight material, much of the new stuff out there is made of bismuth/tin alloys, which while mostly non-toxic, is pricey for what it is.
One of my big rants over the last several years has been about the inadequacy of lead-free solders for aerospace, as well as life-critical applications, namely in control electronics, explosive detonators, and other devices where if something does what it is supposed to at the wrong time, or doesn't do what it's supposed to at the right time, can end badly for the user. RoHS be damned, I still use lead solder. I simply can't account for the possibility of whisker formation or tin pest causing problems. I had this issue a number of years ago with some flashlights, they were soldered using a lead-free solder, and the tin would revert to the alpha form whenever the temperature dropped below freezing, and our gear would simply stop working.
Most silver solders have higher melting points which makes them unsuitable for many electrical applications as it will damage FR4 along with many components while trying to solder. The rather generic lead-free solders do occasionally contain toxic metals such as cadmium, but way less than what you would find in regular eutectic lead solder.