Hello,

I would like to know why is the sea water salty.

It is hard to answer that question in a short form...
Here are some links which will explain it in detail...

1) http://www.utdallas.edu/~pujana/oceans/why.html
2) http://www.palomar.edu/oceanography/salty_ocean.htm
3) http://www.yesmag.bc.ca/Questions/sea.html