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Menu  Q & A: magnets in water  Learn more physics!  Browse our
6408 answers by or search term  Underwater, will a magnet around
a plastic tube move a metal cylinder inside the tube? If so how
strong is the bond and how is this affected by the gap between
the magnet and the cylinder? - victor hunter Yes, there will be
a force so long as you use a magnetic metal, such as iron or
most steels. The water and the tube have virtually no effect on
the force. The force gets weaker if the gap is larger. We can't
tell you the strength of the force without much more
information. You can just measure it without the water first, if
that's easier.  Mike W.  (published on 05/11/11)  Follow-up on
this answer.