Halloo.
yell
to attract and hold the attention or interest of
To attract the public's attention
The perversity of his behavior had begun to attract attention.
Caps in texting or chat means they are shouting. Or Desperately wanting to caught your attention...
Scream and yell the word HELP as loud as you can. Scream, yell, and thrash your arms as much as you can. Yelling and thrashing will attract attention.
yeah, if you're shouting the one word.
Look
The Official Scrabble Dictionary lists lo as an acceptable Scrabble word. It is used to attract attention or to express surprise.
The hungry dogs were making raucous barks to attract the attention of the people.
Roar.
listen