  Jellyfish galaxies are an intriguing snapshot of galaxies undergoing
ram-pressure stripping (RPS) in dense environments, showing spectacular
star-forming knots in their disks and tails. We study the ionized gas
properties of five jellyfish galaxies in massive clusters with Gemini GMOS/IFU
observations: MACSJ0916-JFG1 ($z=0.330$), MACSJ1752-JFG2 ($z=0.353$),
A2744-F0083 ($z=0.303$), MACSJ1258-JFG1 ($z=0.342$), and MACSJ1720-JFG1
($z=0.383$). BPT diagrams show that various mechanisms (star formation, AGN, or
mixed effects) are ionizing gas in these galaxies. Radial velocity
distributions of ionized gas seem to follow disk rotation of galaxies, with the
appearance of a few high-velocity components in the tails as a sign of RPS.
Mean gas velocity dispersion is lower than 50 \kms~in most star-forming regions
except near AGNs or shock-heated regions, indicating that the ionized gas %in
these star-forming regions is dynamically cold. Integrated star formation rates
(SFRs) of these galaxies range from $7~{\rm M_{\odot}~{\rm yr^{-1}}}$ to
$35~{\rm M_{\odot}~{\rm yr^{-1}}}$ and the tail SFRs are from $0.6~{\rm
M_{\odot}~{\rm yr^{-1}}}$ to $16~{\rm M_{\odot}~{\rm yr^{-1}}}$, which are much
higher than those of other jellyfish galaxies in the local universe. These high
SFR values imply that RPS triggers intense star formation activity in these
extreme jellyfish galaxies. The phase-space diagrams demonstrate that the
jellyfish galaxies with higher stellar masses and higher host cluster velocity
dispersion are likely to have more enhanced star formation activity. The
jellyfish galaxies in this study have similar gas kinematics and dynamical
states to those in the local universe, but they show a much higher SFR.
