I can find Raquazzar but I can't capture him/her?

To not let Latios get away use the move mean look or wobbufet (spelling)

To CATCH both Raquazza and Latios use the catch any pokemon cheat wich is this:

When the ball opens press right when it closes press and hold the B button before it rolls to one side, press and hold right......... and there you go!

Well, the best way to catch a Rayquaza is by using a Master Ball or plenty of Timer Balls. Ignore the person who sent in the easy catch cheat. It's totally bogus.

To get Latias, do the same as what you do with Rayquaza, but at the beginning of the battle use Mean Look, or make sure you have a party of Wynauts and Wobbuffets at the ready. To make Mean Look work, your Pokemon's level will have to be 47 or higher. With the Wynaut thing, Latias won't be able to run away because Wynaut's and Wobbuffet's special abilities are both 'Shadow Tag' which prevents the foes escape.

Shoal Cave. At high tide, there's nothing really interesting except you can find some Shoals to bring back to the Old Man. Low Tide is where all the action is.

At low tide you can find a ladder that will take you through a maze, and at the very end you will find an ice part where you can find Snorunts (although they're still rare) and the item known as Nevermeltice.

ITS NOT RAQUAZZAR!!!!!!ITS CALLED RAYQUAZA! Make sure you bring LOTS of ultra balls just in case.Anyway,to get it(Rayquaza has no gender)Have a pokemon use an attack like quick attack.Make sure you dont kill it!!Anyway after the attack wait for it to use rest.

I know it will make it strong again but it will fall asleep!Once its asleep use the ultra balls!I caught my Rayquaza with 1 ultra ball!It was at full power and I caught it just because it was asleep!If you dont like that,get a friend to give you a master ball or try to win first place in the lottery corner in lilycove.You should get a free master ball.
What game do you have?
Sapphire-Latias is a girl.You get her by getting a golbat or any other bat and teach it mean look.Or get a wobbufet and make it super strong!Make sure itsa ability is shadow tag.Try to put her to sleep and then use lots of ultra balls.Or do the same thing that you did with Rayquaza.
Shoal cave is where you get shoal salt,shoal shells,spheals,golbats,Zubats and Snorunts(glalies 1st form).It is located by Mossdeep.To get shoal salt and snorunt(the others are avalaible at all times)go to the cave at 5:00pm or 5:45pm Go look for the all ice room.Look around.

It should be close to six by now which is when snorunt could be caught.For the shoal shells go to the cave at any other time.

First, you have to study Rayquaza's moves before you can make your move:

Fly: Flies up to avoid attack on the first turn and strikes on the next; used to fly to places already visited. (Power: 70, Accuracy: 95%, PP: 15)

Extremespeed: Attacks first. (Power: 80, Accuracy: 100%, PP: 5)

Outrage: Attacks continuously for two to three turns before becoming confused. (Power: 90, Accuracy: 100%, PP: 15)

Rest: Goes to sleep for two to five turns to restore HP and elminate status abnormalities. (PP: 15)

Use a combination of low-power Rock- and Ice- type attacks to whittle his vitality to where you want it, and then start chucking away. If it uses Rest, repeat the process as quickly as you can and try to chuck away while he's still asleep.

As for Latios, you just have to put up with his tendency to flee unless one of your Pokémon know Mean Look, Wrap, Bind, Clamp, Sand Tomb, Spider Web, Block, Fire Spin, or Whirlpool. I recommend using a high-level Sableye or Claydol.