The exercise was to prepare the swimmers in case they need to swim in the dark.<br/><br/>If I had to use 'in case of' instead of 'in case', I would:<br/><br/><span style="color:rgb(0,0,0);">The exercise was to prepare the swimmers in case of having to swim in the dark.</span><br/><br/><span style="color:rgb(0,0,0);">Is that okay?</span><br/><span style="color:rgb(0,0,0);">Thanks.</span>