Every year since 1925 the wild ponies of Assateague Island have been herded by “saltwater cowboys” across a small channel to Chincoteague Island.

A herd of about 150 wild ponies spends most days munching wild marsh grasses — and delighting visitors — on the barrier island of Assateague off Virginia’s Eastern Shore. But once a year, the ponies take a field trip to neighboring Chincoteague Island in dramatic fashion: They swim there.

On Wednesday, the ponies took part in the 92nd annual Chincoteague Pony Swim, part of a week-long Pony Penning and Carnival. Every year a group known as the “Saltwater Cowboys” rounds up the wild ponies, herds them down the Atlantic beaches and swims them across a small channel to the town of Chincoteague, Va. Along the way, the ponies are checked by veterinarians to be sure they’re strong enough to make the…