Chunks of concrete and rusty metal standing taller than an adult at full height dotted the sand on the north end of Tybee Island one warm day last week, but the beachgoers soaking up the sun nearby didn’t seem to mind. In fact, some pitched their beach umbrellas right next to the sand fences that quarantined off the old blocks to try to shield themselves from the wind. Before they were moved to dry land in recent weeks, the concrete and metal chunks had spent the last few decades sometimes submerged, sometimes exposed in the water off North Beach as part of a sea wall and steel groin system. They’ve posed quite the challenge to island officials, who have worked over the years to find the funding and permits to remove them.