Aletius

Hi all, so im trying to get some pokemons and I find myself confused about how the spam of some work, more specific the ones involving surf/fishing. So the Pokemon tab on each map indicates many things about pokemons there: 1-Grass (normal / donator if pink) 2-Blue circle (normal / donator if pink) 3-Blue circle + rod (normal / donator if pink) So i tought that the ones with blue circle spawm by surf and the ones with rod only by fishing. But by fishing i got the ones without rod too. So I guess the ones with rod spawm only with fishing but then i get one of then by surfing...So i click on some to see what the pokedex says and got more confused cause some pokemons dont have the grass or water icon to indicate where they spawn and in the pokemon tab do not indicates rod pokemon. Take for example Lapras on route 21, spawns in all day times, dosnt have the rod on icon and in pokedex its not marked as grass nor surf spawm. Can someone explain how those function works?