Trestle Bridge is a local Delaware River swimming and jumping spot near Portland, in Upper Mount Bethel Township, Pennsylvania, where the river forms the Pennsylvania-New Jersey line at the southern edge of the Delaware Water Gap. The name comes from the area's landmark railroad crossing, the towering Delaware River Viaduct, a long concrete-arch structure that locals nicknamed "Alice" or "Wonderland," and the swimming happens along the river below and around the old bridge crossings, where deeper channels and slower pools form good places to cool off.

This stretch of the Delaware is broad, relatively gentle and popular for tubing, paddling and casual river swimming, with the historic Portland-Columbia pedestrian bridge, one of the last of its kind, crossing nearby into Columbia, New Jersey. As with any big-river swimming, the Delaware deserves respect: current, depth and clarity change with rainfall and dam releases upstream, the bottom is uneven, and jumping from any bridge or structure carries real risk from shallow water and hidden hazards, so many locals stick to wading and swimming from the banks and beaches rather than leaping from the trestle.

The area is an easy day trip from the Lehigh Valley and the Poconos, and it pairs with nearby Delaware River access points like Smithfield Beach upstream. Summer is the season, when the water warms and the river runs lower and friendlier. Trestle Bridge is less a manicured swimming beach than a well-known local river spot, best enjoyed by those who know the Delaware and read its conditions before getting in.