Yes, by using the HM Dive.
To go under water in Pokemon ruby, you must first have i think it is 6 or 7 badges and then have a water Pokemon who can learn dive... then all you need is to get the hm dive, teach it to that water Pokemon and you're all set! hope i helped a little bit =)
you cant go underground but you can go under water by using the move dive. you get dive in mossdeep city
in Pokemon sapphire/ruby you need to go under water in go into the grass it might take a while but keep trying and don't give up.
u cant
go under water in mosdeep city( i think its mosdeep) and keep looking.
you can't, only ruby Pokemon can go to diamod. but diamond Pokemon can't go to ruby
to get to the 8th gym in Pokemon ruby, go to lily cove and surf east a bit then down. theres a a big dive spot. go down using dive. follow the under water hallway until the is an entrance. go in . ure in sotopolis at the gym.
to the 8th gym :p but seriosly i think u go to stooplis meaning u have to go under water about west form mosdeep
you go under water using dive then go into the grass and keep going around in the grass and battling the Pokemon til u find relicanth
You can't go to the moon in any Pokemon game including Ruby You can't go to the moon in any Pokemon game including Ruby
you dont go to jhoto in ruby
there are 200386 Pokemon can be found in Pokemon Ruby if you go to Nintendo Events.