On shellder/cloyster pearls: Actually, yes! If any kind of sediment gets into a mollusk pokémon’s shell, it might create a pearl, even if the pokémon in question isn’t a clamperl. It’s just that shellder and cloyster pearls can sometimes be rarer because they’re more aggressive than clamperl, so the only way to get them is either by raising shellder to release their pearls if asked or by harvesting them from already-dead pokémon.
Also, it’s true that shellder and cloyster are normally found in salt water in most regions, but for some reason, Sinnohan shellder and cloyster can sometimes be found in fresh. So if you live in Sinnoh, those are pretty rare pokémon, but it’s not completely odd that the divers you know are finding them in freshwater ponds. If it’s anywhere else, though, that is a bit weird, yes.
On dratini: Well, like most serpentine pokémon, it’s difficult to tell at a glance, especially if you don’t have more than one specimen on hand to compare. But male serpents will normally have thicker tails that taper more dramatically than females. Or in other words, female serpents generally have thinner tails, and you don’t really notice the slope of the taper until the tail just sort of … ends.
When it comes to befriending them, start off by looking as nonthreatening as possible. Sit down if you can, and talk to the dratini in a calm, soothing manner to get its interest. Let it come to you and offer to play with it—again, in as calm and soothing a manner as you can. Dratini are highly intelligent, so they might get what you’re trying to ask them without you having to do much else. Use food and treats as a last resort; you don’t want to accidentally train this dratini to rely on people as a source of food. On the other hand, if you have a pokémon, maybe let your smallest and/or friendliest one out to show this dratini a potential playmate.
And if it’s a swimming ekans … back away from the body of water carefully but quickly.
The Pokédex According to Bill 
