[TOMT] Average slasher movie with a funny blowjob murder scene

My friend and I were thinking of a horror movie we watched over 5 years ago on TV that really made us laugh in one scene. It was a usual slasher movie set in a party house of young people, and the first victim was a blonde girl who got killed in the kitchen after opening a cupboard with a head in it(?). But the bit we remember is a girl who dives down to give her boyfriend a blowjob in the pool or jacuzzi but while she’s down there the killer cuts his head off in a comical way and she doesn’t realise. Does anyone know what movie this is? It wasn’t famous or anything. Searching it with what I remember is unfortunately giving me sus results. 😅