Level 100 Statistics (see level 5, 50, 100)
It's no surprise that Shell Smash would be abused by Pokemon who get Baton Pass—and Gorebyss is no exception. Gorebyss gets a niche in Ubers over other Shell Smash users because of her wonderful ability, Swift Swim, which makes use of the most common weather in Ubers—rain. Her Water-type STAB also makes use of rain, boosting Surf and Hydro Pump by 50%. However, Gorebyss has no true defenses to speak of, and she receives very tough competition for Smeargle, who can use Spore in conjunction with Shell Smash and Baton Pass.
Gorebyss is one of the best Baton Pass users in the tier, because with Shell Smash she only requires one turn of setup. The benefit she gets over Smeargle is her ability, Swift Swim. Rain is very common in Ubers, and not only does it double Gorebyss's Speed, but it also pumps up Surf's power. In rain, Gorebyss can outspeed and revenge kill Mewtwo and Pokemon slower than her, as she reaches 406 Speed. Shell Smash along with Baton Pass is a strategy that is very effective, and it is sometimes very hard to stop. Because Shell Smash boosts Attack, Special Attack, and Speed, once Gorebyss has Baton Passed to the appropriate sweeper, it's nearly guaranteed that your opponent will have a tough time against it. However, Gorebyss is very frail, so in order to get this strategy working Gorebyss must come in and out very quickly.
Team Options & Additional Comments >>>
Gorebyss doesn't really have any other options. Gorebyss can only land some damage with Surf or Hydro Pump, and Ice Beam. Gorebyss should never invest in any defense, as Gorebyss's defenses are pathetic by Ubers standards.
Checks and Counters
The first step in countering Gorebyss is removing rain. Groudon is the best option since sun weakens Gorebyss's STAB moves, but Tyranitar and Hippowdon are also options. Gorebyss is very frail, so hitting hard and hitting fast should do the job. Priority users, such as Arceus and Giratina-O, can bypass Gorebyss's boosts and strike very hard, with or without the Defense drop. Dialga, defensive Kyogre, and Giratina-O can phaze Gorebyss with Dragon Tail or Roar, respectively. Kyogre gets the bonus of resisting all of Gorebyss's moves, and Dialga can tank them due to its bulk. Gorebyss can only Baton Pass once without Defense drops, so if you can scare her out, then you have probably avoided the worst.