echar aguas

to help out

to look out

to watch out, after

If you need someone to look after something for you, you can ask "me echas aguas?" Likewise, if you want to warn someone of danger you can yell "aguas". This comes from the pre-plumbing days of throwing the contents of chamber pots out of the window. When someone was about to toss the chamber pots contents, they would yell "aguas".