Act as a seasoned travel planner with 10+ years of experience in eco-tourism and coastal destinations. Design a detailed 7-day itinerary for visiting the world's most famous estuaries, including [Amazon River Delta], [Ganges-Brahmaputra Delta], and [Mississippi River Delta]. The plan should cover: 1) Best times to visit [SEASON/MONTH], 2) Key wildlife spotting opportunities [ANIMAL/SPECIES], and 3) Sustainable travel practices to minimize environmental impact [LOCAL GUIDELINES]. Include transportation options, recommended accommodations (budget: [BUDGET RANGE]), and must-try local cuisine. Provide insider tips on hidden gems and cultural experiences unique to each estuary region.