  The recently discovered (Li${_{1-x}}$Fe${_x}$)OHFeSe superconductor with
$T_c$ about 40K provides a good platform for investigating the magnetization
and electrical transport properties of FeSe-based superconductors. By using a
hydrothermal ion-exchange method, we have successfully grown crystals of
(Li${_{1-x}}$Fe${_x}$)OHFeSe. X-ray diffraction on the sample shows the single
crystalline PbO-type structure with the c-axis preferential orientation.
Magnetic susceptibility and resistive measurements show an onset
superconducting transition at around ${T_c}$=38.3K. Using the magnetization
hysteresis loops and Bean critical state model, a large critical current
${J_s}$ is observed in low temperature region. The critical current density is
suppressed exponentially with increasing magnetic field. Temperature
dependencies of resistivity under various currents and fields are measured,
revealing a robust superconducting current density and bulk superconductivity.
