Visit the Roman ruins. Tyre has two main archaeological sites. Al-Bass features one of the largest Roman hippodromes ever excavated, along with an ornate necropolis. Al-Mina, closer to the old town, has Roman colonnades, Crusader remains and the ancient harbour area. Both are worth exploring.
Swim at the beach. Tyre has the best public sandy beach in Lebanon -- a long, clean stretch of sand with turquoise water. Unlike most of the Lebanese coast, it is free and genuinely pleasant. Ideal for a relaxing afternoon.
Explore the old town. The narrow streets of Tyre's old city have a working fishing-port character. Colourful boats line the harbour, fishermen mend nets, and small restaurants serve fresh catch. It is less polished than Byblos but more authentic.
Go diving. The waters off Tyre have good diving, with underwater ruins, reefs and clear water. Hiram Scuba Diving club operates from the Mina area, offering equipment rental and guided dives. Sites range from shallow reef dives (11-20 metres) to deeper explorations including "The Crater" (36-60 metres) and underwater freshwater springs.
Visit the Sea Life Museum. A small museum with local marine exhibits, worth a quick stop if you are in the area.