This paper highlights the impact on extension of dry dock due to deepening of floor slab at an island in the Indian Ocean. Existing dry dock is of 90 × 20 × 7.5 m inner dimension and is used for repairing vessel of size 75 × 10.5 × 4.5 m. In order to accommodate more number of vessels coming for repairing purpose, extension of existing dry dock with additional length of 90m is proposed. Hence new inner dimension is 180 × 20 × 7.5 m. It is noticed that the existing floor slab level (−) 4.00 m Chart Datum (CD) of dry dock had changed to (−) 5.00 m CD due to variation of sea tidal level after devastation of Earthquake and Tsunami in 2004. Thus the water depth of proposed extension of dry dock walls has to be increased from 7.50 m to 8.50 m. This impacts the design of components of proposed dry dock and the details of existing dry dock wall and proposed dock wall are discussed in this paper. © 2019 Taylor & Francis Group, London.