Use Surf on Route 205 and you'll easily find a Tentacool.
you do not find dialga in Pokemon pearl
Most Water Pokemon can learn surf in Ruby, like tentacool or wingull.
Tentacool evolves on Lvl. 30 into Tentacruel.
Tentacool evolves at level 30 into Tentacruel.30
Use Surf on Route 205 and you'll easily find a Tentacool.
In the national pokedex it's tentacool, and in the pearl pokedex it's misdreavus.
Certain Pokemon learn it by leveling up, such as tentacool. There is no TM and no Tutor, so you might want to check serebii.net's attackdex to find out what Pokemon can use it and how they learn it.
it is Tentacruel
In Pokemon Diamond, Pearl, and Platinum you can find Tentacool in almost any large body of water. Once you get the move Surf from the Pastoria Gym go back to Sandgem town. You have to teach a Pokemon surf first, pretty much all Water type Pokemon can learn it. Then go down to the beach and use surf in the water. Swim around a bit and you're bound to run into a Tentacool.
Tentacools and Tentacruels are often found while surfing. Try areas around Pastoria City.
if you have surf then anywhere with water
In RSE you can find Tentacool on Route 103.
you do not find dialga in Pokemon pearl
Pokemon 72 is Tentacool.
you can't you have to catch a tentacool then it evolves at level 30.
With the old rod you have the lovely selections of Magikarp and Tentacool