Whirl islands are in the johto region which is not in firered.
The Whirl Islands
In the whirl pool islands
in whirl islands you have to have surf
to find lugia go to the 4 whirl islands
You can find Horsea around Whirl Islands, and I suppose you can evolve it from there.
You can find Seels all the time in the Whirl Islands
Go to each to find out.
seafoam islands
Staryu is a water type Pokemon. In Pokemon FireRed, it is possible to find lots of Staryus in the Seafoam Islands.
In Pokemon Heartgold, Lugia can be found at the top-right island of the Whirl Islands Area. It's at Lv. 70 so prepare.
To get mantine in crystal and gold surf around the whirl Islands
You can find Luigia at the Whirl Islands, you have to go quite deep.