  Star-forming, H$\alpha$-emitting clumps are found embedded in the gaseous
tails of galaxies undergoing intense ram-pressure stripping in galaxy clusters,
so-called jellyfish galaxies. These clumps offer a unique opportunity to study
star formation under extreme conditions, in the absence of an underlying disk
and embedded within the hot intracluster medium. Yet, a comprehensive, high
spatial resolution study of these systems is missing. We obtained UVIS/HST data
to observe the first statistical sample of clumps in the tails and disks of six
jellyfish galaxies from the GASP survey; we used a combination of broad-band
filters and a narrow-band H{\alpha} filter. HST observations are needed to
study the sizes, stellar masses and ages of the clumps and their clustering
hierarchy. These observations will be used to study the clump scaling
relations, the universality of the star formation process and verify whether a
disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents
the observations, data reduction strategy, and some general results based on
the preliminary data analysis: the UVIS high spatial resolution gives an
unprecedented sharp view of the complex structure of the inner regions of the
galaxies and of the substructures in the galaxy disks; we found clear
signatures of stripping in regions very close in projection to the galactic
disk; the star-forming regions in the stripped tails are extremely bright and
compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan
for the project.
