  Inertial particles (i.e. with mass and of finite size) immersed in a fluid in
motion are unable to adapt their velocities to the carrying flow and thus they
have been the subject of much interest in fluid mechanics. In this paper we
consider an ocean setting with inertial particles elastically connected forming
a network that floats at the interface with the atmosphere. The network evolves
according to a recently derived and validated Maxey--Riley equation for
inertial particle motion in the ocean. We rigorously show that, under
sufficiently calm wind conditions, rotationally coherent quasigeostrophic
vortices (which have material boundaries that resist outward filamentation)
always possess finite-time attractors for elastic networks if they are
anticyclonic, while if they are cyclonic provided that the networks are
sufficiently stiff. This result is supported numerically under more general
wind conditions and, most importantly, is consistent with observations of rafts
of pelagic \emph{Sargassum}, for which the elastic inertial networks represent
a minimal model. Furthermore, our finding provides an effective mechanism for
the long range transport of \emph{Sargassum}, and thus for its connectivity
between accumulation regions and remote sources.
