In　order　to　investigate　the　damage　mechanism　of　dams　subjected　to　underwater　contact　explosion,　firstly,　an　experimental　program　was　conducted　with　six　concrete　slabs　and　two　explosive　quantities.　The　test　results　showed　that　the　diameter　and　depth　of　the　crater　on　the　front　and　back　surface　of　the　concrete　slab　increased　with　increasing　explosive　quantity　with　radial　and　circular　cracks　generated.　Three　different　concrete　material　models　were　tested　and　it　was　found　the　CDP　model　was　most　suitable　in　simulating　concrete　subjected　to　underwater　explosion.　The　calibrated　models　were　used　to　conduct　parametric　studies　to　study　the　effect　of　explosive　quantity,　slab　thickness,　and　transferring　medium　(water　or　air).　Numerical　analysis　results　showed　that　the　diameter　and　depth　of　the　crater　on　both　the　front　and　back　surface　of　the　concrete　slab　decreased　with　increasing　slab　thickness　and　decreasing　explosive　quantity.　In　addition,　the　damage　caused　by　the　air　contact　explosion　was　smaller　and　more　concentrated　in　the　detonation　center　compared　with　underwater　contact　explosion.　Finally,　a　gravity　dam　and　an　arch　dam　were　modeled　to　study　the　effect　of　detonation　depth　and　water　level　on　the　damage　distribution　pattern　of　the　dams.　Based　on　the　results,　recommendations　were　provided　for　the　anti-explosion　protection　design　of　hydraulic　structures.　©　2023　Elsevier　Ltd