Just Southeast of Sootopolis City, it's underwater so make sure you 1)beat Liza & Tate, 2) got HM08 Dive from Steven
the stolen sub is southeast of sootopolis city and west of ever Grande city but you have to have dive to find it.
at lilycove city is where i found it out
there is no sub. only on Pokemon sapphiere and emerald. you have to defeat Team Magma, not Team Aqua.
After you find the stolen submarine in Pokémon Emerald you must go to Mossdeep city. There you will obtain the HM Dive.
Its underwater and on the map its left and down from evergrande city
it is in sootopolis city but under water in satapolis city Museum
first beat up team magma in cave by lavaridge then fly to lilycove and the two thugs tell you arche is at slate port to steal sub. after you get there you here cosmo talking to media and sub gets stolen. after that go to lilycove and you are able to get. in
Mt. Pyre on the route going to Lilycove from Fortree. There will be a lake that you can Surf on to get to the mount in the middle.
go to lilycove and head to the beach and surf up and you'll see a cave go threw it and you'll sea the sub at the end.
its not an emerald its RAYQUAZA the main legendary Pokemon in Pokemon emerald.
You cannot get a Yanma in Pokemon Emerald, as only Hoenn Region Pokemon can be found in Pokemon Emerald.
There is no PalPark in Pokemon Emerald.