water boils..spontaneous reaction

Considerable heat is needed to make steam, so I suppose that is the meaning of endothermic. I don't see the link to spontaneous reaction. Perhaps you can give more details or a hint.
I have heard that the water can get several degrees above the boiling point, then boil vigorously for a few seconds, so perhaps it is not always a spontaneous reaction? Neil

"Spontaneous" always depends on conditions, and heat energy is only one consideration, I think. The gaseous state of water at a pressure of one atmosphere and a temperature of over 100 C is thermodynamically favored, so it is a spontaneous reaction.

Though I could be wrong. I'm not much of a chemist.

you are right.And spontaneous means that the reaction occurs under standard conditions of heat and atmosphere pressure ( 25 - 1 ) with plenty of air or oxgene .Provided that it takes enough time to happen and the total heat of the system should be off ( exothermic ) .I think water here is an exempt .