It was probably originally a fish trap to trap fish when the tide came in and went out. But the sea level would have still needed to be lower for it to work.
Without knowing the direction it runs (parallel with or perpendicular to the coast) there’s no basis to say that. The Romans used artificial pools that would accumulate fish during high tide and strand them in low tide, and some of those are still visible. The method antedates the Romans.
The ones in Crete, contrary to claims, are not a good way to measure sealevel change, because the Aegean is known for seismic activity and changes in ground and seabed levels, reports of this go back to antiquity.
https://www.google.com/search?q=Roman+fish+traps+coast+of+mediterranean