The best thing you can do is use a master ball or weekin it then give it a ubnormal weekiner EX/ poisin or sleep
Marine Cave
Kyogre Is Not Avalible In Pokemon Ruby. Just In Pokemon Sapphire/Emerald
you really should get emerald cause Pokemon ruby and Sapphire are separate and emerald is those 2 put together so instead of getting ruby and getting groudon just get emerald and you can get groudon and kyroge and newer Pokemon
you need the blue orb which is only obtainable in heartgold
Yes, You can catch Groudon in Pokemon Emerald.
You can't catch one in Pokemon Emerald.
No you cannot catch Entei in Pokemon Emerald.
You can't catch a Bellsprot in Pokemon Emerald. You trade it from Pokemon Leafgreen!
There are many Pokemon you catch that are similar in sapphire and emerald but there are many Pokemon emerald can only get and not sapphire.
Cressilia is a 4th generation Pokemon so you can't catch it in Pokemon Emerald.
You can't catch or obtain other trainers Pokemon in emerald.
you cant. You can only catch it in Pokemon emerald, but, you cant catch latias in emerald.