Denia and Xabia/Javea are a compact Costa Blanca base for local boat dives, rocky snorkel coves, relaxed freedive mornings and strong non-diver days. The headline is Cabo de San Antonio Marine Reserve, a protected cape between both towns where posidonia meadows, boulder fields, sandy passages, caves and gorgonian-covered walls attract groupers, octopus, morays, nudibranchs and seasonal pelagic life. This is not a liveaboard destination. Plan it as a shore-and-day-boat trip with a rental car, local dive center permits, early cove starts and flexible routing around wind. Summer brings the warmest water and busiest beaches. September and October are the sweet spot for warm sea, clearer coves and easier logistics. Non-divers can hike Montgo, visit Cova Tallada, explore Denia Castle, wander Xabia old town and take responsible whale-watch trips during the fin whale migration season.