I don't know what sorts of leads or theories they were working from, maybe he was probing into the submerged sand beyond low tide line for something.
What is your explanation of the footage of this strangely dressed man wading in the sea at night with a pole?
If anyone knows the background to this team and their antics, it would be interesting to start a thread on it. Anyone?
At the moment, working with the tiny scraps I have, here is my stab at an answer.
First, the person had a genuine belief that something related to the case was buried there, (e.g. a body or clothes) some distance under the surface of the sand, and the person was genuinely testing this out.
Second, the quote says footage, so I assume we are talking video here. And that raises the possibility it is part of a stunt, simply to 'justify' costs and expenses, as in 'We were very diligent. Even making sure the beach was fully checked out!'