I do not think we have ascertained that they were searching for a dead body. I suspect they thought they were searching in the hopes it was a live body.
The question is - what was their plan if they had found a live person in the water at night? Try an ad-hoc letdown over the water to put a skid in the water??? How well would that have gone? We have all seen instances on these pages where pilots have felt obliged to try things outside their experience or capabilities when life is at stake - sometimes they get away with it but the majority of cases end in tears.
Yes, get a helicopter up to have a look but mobilise ground/water units to assist in case quick action is needed to preserve life - the helicopter itself is just a location tool if they can't carry out a rescue.