I have another D-Day question on the Normandy landings..what were those "X" shaped metal barrier things sitting on the beach?

They were meant to prevent landing craft from getting close enough to the beaches to offload troops.

Keep the landing craft away from the beach. A soldier with a fifty pound pack can wade through water only so deep especially with a four or five foot swell crashing in from behind. So the further away from the beach you could stop the landing craft, the greater the chance the invading soldiers would literally drown before they made it to the beach.

They were designed to stop any men or equipment from invading Nazi-Occupied Europe.

They were to stop people parking on the beach.

at high tide they rip open the bottom of landing craft

Anti-tank devices (that had an added benefit of threatening the hulls of ships (like landing craft) when the tide was in).

Slave labour put them there under the direction of Germans.

They were put there by the Germans to make it harder to beach Allied landing craft. Made the landing boats full of men much easier to shoot at.

They were anti-tank obstacles

They were called Czech hedgehogs

https://en.wikipedia.org/wiki/Czech_hedgehog