What does this Pokemon Trainer mean by saying the player is "SHELLOS"?

What does this Pokemon Trainer mean by saying the player is "SHELLOS"? - Hand of man with racket and ball on tennis table

While challenging the Battle Factory in Johto's Battle Frontier, a Pokemon Trainer battles with you, and tells you (after defeating him):

You're just SHELLOS, if I say so myself.

I am Gen I & II Pkmn Trainer, so I don't really know what the characters of the new Pokemon are (for example, I would know that a Blissey would care for others). What does that Trainer mean? In other words, what does SHELLOS mean in this context?

enter image description here

After being defeated:

enter image description here






Pictures about "What does this Pokemon Trainer mean by saying the player is "SHELLOS"?"

What does this Pokemon Trainer mean by saying the player is "SHELLOS"? - Pokemon Go Application on Smartphone Screen
What does this Pokemon Trainer mean by saying the player is "SHELLOS"? - Person Holding Blue Flaglet Holding Golf Driver
What does this Pokemon Trainer mean by saying the player is "SHELLOS"? - Man trainer fixing leg position of woman player in curling





Pokemon Legends: Arceus SHELLOS of the EAST and WEST




Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.

Images: Andrea Piacquadio, Pixabay, Jopwell, SHVETS production