A swimmer training apparatus includes a housing having a rotatable spool mounted therein and defining a longitudinal spool axis. The rotatable spool includes a cylindrical outer surface and a spooler is mounted to the housing and adapted to axially advance a swimmer tethering line along the cylindrical outer surface during playing out or taking up the swimmer tethering line. The swimmer training apparatus further includes a torque transfer device coupled between a motor and the rotatable spool and including a magnetic field generator configured to generate a magnetic field. The torque transfer device further includes a rotatable mechanism fixed to rotate with the rotatable spool and a rotatable mechanism fixed to rotate with the motor. One of the rotatable mechanisms includes a magnetically permeable medium adapted via interacting with the magnetic field to transfer a torque between the first rotatable mechanism and the second rotatable mechanism during rotating the rotatable spool. A torque control system for the swimmer training apparatus includes an electronic control unit configured via software and/or hardware control to implement an operating method for training or evaluating performance of a swimmer.