A truly irreplaceable waterfront estate where timeless craftsmanship meets exceptional luxury. Originally built in 1928 and completely reconstructed in 1993/1994, this remarkable 5,700 sq. ft. residence is set on a private half-acre of deep-water waterfront in coveted West Islip, just minutes from Babylon Village & LIRR Main Line station. With incredibly low taxes, flood insurance under $1,500 per year, and grandfathered features that could never be approved under today's zoning, DEC, and New York State regulations, this is a once-in-a-generation offering. Designed for the discerning waterfront lifestyle, the property features a legal detached guest cottage complete with a studio apartment, full bath, washer/dryer, separate electric meter, and private waterfront deck—ideal for guests, extended family, or income-producing opportunities. Boating enthusiasts will appreciate two protected 35-foot boat piers with full pier walls, five oversized boat slips, 40 feet of private beach, deep water directly behind the property, and an unbeatable location just 500 feet from the open Great South Bay—eliminating the long canal runs found at most waterfront homes. Spanning three full levels of beautifully appointed living space, the 16-room main residence offers seven spacious bedrooms and 3.5 baths. Rich architectural details include exquisite original moldings, stunning 5/4 oak flooring, recessed lighting throughout, and meticulously restored circa-1930s light fixtures rewired for modern living. The luxurious primary suite opens through French doors to a private balcony overlooking the heated saltwater Gunite pool and tranquil river. A dramatic second-floor office boasts soaring 15-foot ceilings and sweeping views of the Great South Bay, while the expansive third-floor entertaining level features a custom wet bar, creating the ultimate game room and gathering space. The outdoor living experience is equally spectacular. Reconstructed in 2021, the commercial-grade heated Gunite pool features a saltwater system and is surrounded by an expansive entertaining area with a built-in Jacuzzi, cascading waterfall, river rock wall, and an oversized covered porch designed for effortless indoor-outdoor living. Westerly exposure delivers breathtaking sunset views over the water, while the rare absence of rear neighbors provides exceptional privacy. Recent improvements include Polyglass siding, ductless air conditioning, rebuilt decks and terrace, LED exterior lighting, and a beautifully renovated primary bathroom completed in 2025. Additional highlights include an eight-camera security system, a cobblestone driveway accommodating six vehicles, a two-car-deep garage, and rental income from the guest cottage to help offset carrying costs. Properties of this caliber simply cannot be recreated. Combining historic character, modern luxury, irreplaceable waterfront amenities, extraordinary boating access, and an unrivaled location, this is one of West Islip's most exceptional waterfront estates.