Do you know that you need to get old? No it just happens.

Even some single-celled organisms have light-sensitive photoreceptors as a means of regulating circadian rhythms - such as, in the earliest examples, moving to a place where photosynthesis would be most efficient. While these are capable only of sensing the presence of ambient light, it's not hard to imagine how evolution may have favoured organisms which, through mutation, developed increasingly complex eyes - for example, an organism capable of detecting a dark patch in the ambient light surrounding it would be able to take evasive action in case that patch was a predator; such an organism would therefore have an advantage over other individuals which did not share that ability. Further mutation might then allow future generations of the organism to see food, thus giving them another advantage - and thus, the eye would evolve into the many forms we see today.

Not sure if this is a serious question, but a serious answer would be that the precursor of the eye began before fish even evolved. Photosensitive cells were and are used by bacteria for simple actions, such as guiding it to light. Useful for simple multicellular life as it began to leave the depths of the oceans and adapted to make use of light for a variety of reasons. These primitive eyes are what eventually evolved into the complex eyes we know today. It's highly unlikely that any complex lifeforms evolved without having eyes or even photosensitive cells to one day having functional eyes through a random mutation. Like many traits, eyes evolved independently many times.. but life with eyes had primitive ancestors with photosensitive cells.

An eye would not evolve in isolation.