The devastating 2004 Indian Ocean tsunamiTsunami significantly impacted the Chennai coast, affecting both the environment and marine life. Here we are trying to check the impacts of the tsunami on the Chennai coast, sea-level riseSea level rise, shoreline shift, and effects on turtles (Olive Ridley). A 4.18 mm/year rise in sea level was observed over the Chennai coast from 2000 to 2010. Shorelines were extracted for 2000, 2004, 2005, and 2010 using the CoastSat tool, and the short-term analysis was carried out using the Digital Shoreline Analysis System (DSAS) to understand the before and after of the tsunami shoreline shift on the Chennai coast. The study divided the 86 km shoreline from Uthandi Beach to the North Tamil Nadu Border into six zones. All the zones experienced erosion due to tsunami events from 8.46 to 74% of their shoreline during 2004–2005. Due to the rebuilding of coastal zones post-tsunami, shoreline accretion was seen in 59–96% of the area from 2005 to 2010. From 2000 to 2010, the Students’ Sea TurtleSea turtle Conservation Network collected data on turtle nesting along the Chennai coast (Neelankarai to Adyar, 7.5 km) to assess the impact of the 2004 tsunami2004 tsunami. A negative trend in hatching success (− 2.22%) and egg density (− 0.6355) was observed, with hatching success plummeting from 62.8 to 24% post-tsunami (2004–2005). The event caused significant disruption to the coast and turtle habitats, highlighting the need for conservation efforts against natural and human threats.