In the weeds were you can find when you dive (rare)
NO.
it doesn't evolve in Pokemon ruby.
Tentacool, Relicanth.
No only in ruby and sapphire and emerald.
Dive somewhere on the sea routes and in the grass down there you can sometimes find relicanth along with clampearl.
Relicanth is rare. They'll only appear if you go underwater on Routes 124 and 126.
Catch Clamperl, Chinchou and Relicanth most of these Pokemon hold shards
Just dive underwater and find grass where relicanth is and use sweet scent.
geodude, graveler, rhyhorn, relicanth, regirock, nosepass,
Relicanth is a Water and Rock type Pokemon that first appeared in the third generation of games. In Pokemon Ruby, it can be found underwater, although it is quite rare and will only show up one out of every twenty encounters with wild Pokemon.
You can't catch Relicanth. You have to trade from Ruby, Emerald, Sapphire or any other game that has him captured.
its not the best but it can help you find the regi's on emerald and ruby & saphire