Objects that float at the interface between a liquid and a gas interact because of interfacial
deformation and the effect of gravity. We highlight the crucial role of buoyancy in this interaction,
which, for small particles, prevails over the capillary suction that often is assumed to be the
dominant effect. We emphasize this point using a simple classroom demonstration, and then derive
the physical conditions leading to mutual attraction or repulsion. We also quantify the force of
interaction in particular instances and present a simple dynamical model of this interaction. The
results obtained from this model are validated by comparison to experimental results for the mutual
attraction of two identical spherical particles. We consider some of the applications of the effect that
can be found in nature and the laboratory