It is exothermic. Exothermic reaction is a reaction that gives out heat and energy. Sodium is a highly reactive metal that is found in group 1 in the periodic table. We all know that all group 1 elements(alkali metals) are usually stored in inert liquid like oil to prevent contact with air and water so as to prevent an explosion. An explosion is a form of a exothermic reaction since it gives out heat and light. Hence, the reaction between Na and water is an exothermic reaction.
Have a nice day ahead.