Within the scope of Mandarin Oriental Bosphorus Hotel Project, foundation piles and diaphragm wall works have been completed as of August 2018. Project site locates in Kuruçeşme, along the shoring line of Istanbul Bosphorus and will be the deepest and largest excavation pit constructed under water when it is completed. The depth of the excavation; totally under water will be 24.5 m at the seaside along the shoreline of Bosphorus and 31.5 m at Muallim Naci Road side. A hybrid shoring project, consisting of top-down and bottom up with steel strut techniques, has been prepared and applied for safe excavation without damaging surrounding roads and buildings. Within the scope of the project; 21,600 m2 of diaphragm wall having a depth reaching 60m; 10,900 m of foundation piles and 10,100 m of top-down piles were constructed. Furthermore, at the road side of the working area, 2,500 m of high capacity anchors were designed. Six static tensile pile load tests were conducted and excavation safety has been controlled with instrumental observations, by inclinometer, settlement points and coordinate check points.