The first Electric-type Pokemon you'll likely encounter will be Pikachu in Viridian Forest, which does not require Surf. It is rare, so several encounters may be needed. The next Electric-type Pokemon you can get before Surf is Jolteon. You can acquire an Eevee in Celadon City as a gift, but a Thunderstone is required. The rest of the Electric-type Pokemon will need Surf to reach them.
Find a Pikachu on red or blue, find the surfing hm, teach it surf, trade pikachu with another pokemon, and you have a surfing pikachu.
There are three Pokemon you can catch without a rod on Route 132 (by surfing): Tentacool, Pelipper and Wingull.
You can find Pokemon in grass, caves, fishing or surfing.
In The grass or surfing in the water.
fishing or surfing
In the waters of Lilycove. (You have to fish. No surfing.)
surfing, in tall grass, or in a cave.
By surfing or using a fishing rod
Gastrodon can be found in: Surfing on: Route 205, 212, 213, Pastoria, Canalave, Valley Windworks And also (without Surfing): Route 218., 214 and Iron Windworks
You can find them by surfing and fishing.
Find it while surfing or fishing with the super rod in most water areas.
In Pokemon Silver you can find Wooper in Route 32 but only at night and you can also find it in the Ruins of Alpha in both the grass and in the water but water-wise only via Surfing on a Pokemon and in the Union Cave you can find it in the cave as well as by surfing on the water.