  High-contrast imaging (HCI) observations of exoplanets can be limited by the
island effect (IE). On the current generation of telescopes, the IE becomes a
severe problem when the ground wind speed is below a few meters per second.
This is referred to as the low-wind effect (LWE). The LWE severely distorts the
point spread function (PSF), significantly lowering the Strehl ratio and
degrading the contrast. In this article, we aim to show that the focal-plane
wavefront sensing (FPWFS) algorithm, Fast and Furious (F&F), can be used to
measure and correct the IE/LWE. We deployed the algorithm on the SCExAO HCI
instrument at the Subaru Telescope using the internal near-infrared camera in
H-band. We tested F&F with the internal source, and it was deployed on-sky to
test its performance with the full end-to-end system and atmospheric
turbulence. The performance of the algorithm was evaluated by two metrics based
on the PSF quality: 1) the Strehl ratio approximation ($SRA$), and 2) variance
of the normalized first Airy ring ($VAR$). Random LWE phase screens with a
peak-to-valley wavefront error between 0.4 $\mu$m and 2 $\mu$m were all
corrected to a $SRA$ $>$90\% and an $VAR\lessapprox0.05$. Furthermore, the
on-sky results show that F&F is able to improve the PSF quality during very
challenging atmospheric conditions (1.3-1.4'' seeing at 500 nm). Closed-loop
tests show that F&F is able to improve the $VAR$ from 0.27 to 0.03 and
therefore significantly improve the symmetry of the PSF. Simultaneous
observations of the PSF in the {optical} ($\lambda = $ 750 nm, $\Delta \lambda
=$ 50 nm) show that during these tests we were correcting aberrations common to
the optical and NIR paths within SCExAO. Going forward, the algorithm is
suitable for incorporation into observing modes, which will enable PSFs of
higher quality and stability during science observations.
