New details on the title have appeared in the latest issue of Official PlayStation Magazine UK (it's the cover game), which explains how an Underworld level based in the ruins of a Mayan city is "jammed with detail and lashed with rain".
"Every crack in the architecture's running with shiny hid-def H20, and it'll actually affect Lara's progress - the water makes surfaces slippery, meaning she'll occasionally need to address her grip or risk falling off".