Nestled on the coveted Cobb Isle in Water Mill, this exceptional estate commands 325 feet of spectacular waterfront on Mecox Bay, with sweeping vistas that extend to the Atlantic Ocean. Known affectionately as "Ondine", this is a rare offering of timeless luxury-effortlessly blending sophisticated living with the tranquility of its idyllic setting. Privately sited on a 1.3-acre± peninsula behind a gated entry, with irreplaceable positioning, the estate captures the essence of true Hamptons waterfront living-where legacy, lifestyle, and location converge. Thanks to its grandfathered footprint, Ondine offers sightlines, vistas, and a connection to the bay that no new build can replicate. This singular advantage secures its place among the Hamptons' most valuable and enduring estates. Custom-built to celebrate its unrivaled surroundings, the 7,300 SF± residence delivers effortless flow across open, light-filled living spaces, all meticulously oriented to maximize panoramic water views. Architectural highlights include a grand double-height limestone foyer, Venetian plaster finishes, cove lighting, and a graceful curved staircase-all underscoring the estate's bespoke craftsmanship. Two state-of-the-art kitchens, equipped with top-of-the-line appliances and bespoke finishes, cater effortlessly to both intimate family living and grand-scale entertaining. The expansive primary suite, with two sitting rooms, dual fireplaces, and a private gym, creates a sanctuary of comfort and refinement. Five additional ensuite bedrooms and a total of nine full bathrooms are purposefully designed to showcase awe-inspiring views throughout. Outdoor living unfolds seamlessly across expansive terraces, anchored by a waterside heated gunite pool surrounded by lush gardens. A deeded dock offers direct access to boating, paddleboarding, and jet skiing-privileges that elevate everyday life, with Scott Cameron Beach, Flying Point Beach, and Mecox Beach only minutes away by water. Completing the lifestyle amenities are an outdoor shower, a tiled and heated three-car garage with air conditioning-ideal for car enthusiasts-and generous storage for recreational gear. Whether entertaining on a grand scale or savoring quiet, everyday moments, Ondine provides a lifestyle without compromise-and the perfect backdrop for creating lasting memories. Cobb Isle Road is situated in the prestigious Water Mill Estate section, one of the Hamptons' most coveted addresses. Just 2.6 miles from Southampton Village's Main Street and 1.6 miles from the pristine Flying Point Beach, privacy here is paramount, yet conveniences remain effortlessly within reach. This is not just a home-it is a rare investment in irreplaceability. With no comparable opportunity to secure such proximity to the water, paired with immediate access to a fully realized luxury lifestyle (free from the multi-year hurdles of permitting and construction), 54 Cobb Isle (Ondine) stands alone. For those who seek to own what cannot be recreated-and to live immersed in nature's finest artistry-Ondine offers a magical, timeless opportunity for its next visionary steward.