The question of the degree of harm which is caused by "bad guys" dropping plutonium into the sea is not a simple question; the radioactive power pack containing plutonium-238 which was intended for use in space for the Apollo 13 moon mission was wrapped in a heat-resistant package which is likely to prevent leaking of plutonium for a very long time. However, plutonium released in the form of the nitrate or fine powder is likely to absorb onto mineral particles such as silt. Depending on the exact conditions this absorption onto silt could either tend to fix the plutonium in soil or the silt at the bottom of a lake (or sea), or it could enable the plutonium to migrate from one location to another with greater ease.