Tentacool is a decent Pokemon in the LC metagame as it has a few traits that let it stand out from the rest. For instance, its usable Special Defense stat and typing make it a solid choice for a special wall, while its Poison typing makes it an asset to almost all teams as it allows Tentacool to absorb Toxic Spikes. Tentacool also has access to amazing support moves such as Rapid Spin, Toxic Spikes, and Knock Off, and its base 70 Speed is pretty good for a spinner. Tentacool's ability, Liquid Ooze, gives it a niche against Drain Punch users such as Timburr and Mienfoo. However, like most other Pokemon, Tentacool has its shortcomings. It has a terrible Defense stat, which leaves it vulnerable to almost any non-resisted physical move; its offenses aren't anything to write home about either. All in all, Tentacool is a viable Pokemon that stands out as a reliable and effective spinner.
With access to Toxic Spikes and Rapid Spin, coupled with a good Special Defense stat, Tentacool can effectively run a support set. Tentacool's high Special Defense stat lets it check special sweepers, such as Snover, but special sweepers that carry a boosting move, such as Nasty Plot Misdreavus, can set up on and KO Tentacool as it can't do much apart from Toxic stall them. Toxic Spikes is an important move on this set as it can potentially end up poisoning all your opponent's Pokemon, which stall teams greatly appreciate. Toxic Spikes can also cut short the sweeps of setup sweepers such as Drilbur by reducing their survivability. Rapid Spin is an essential move on almost any team as entry hazards are very common in the current metagame. Knock Off is a very useful move in a metagame filled with Pokemon dependent on Eviolite to perform their duties effectively; it can also remove other important items such as Choice Scarf and Life Orb. The last slot is reserved for an offensive move to ensure that Tentacool isn't completely shut down by Taunt and is not total setup fodder. Scald is a good STAB move as its burn chance can cripple physical attackers; it also severely dents Ground-types, such as Hippopotas, Drilbur, and Diglett. Giga Drain hits Chinchou and Staryu for decent damage and can potentially give Tentacool a form of recovery, but it is otherwise a weak attack.Team Options & Additional Comments >>>
Tentacool can run Icy Wind to lower the opponent's Speed stat, which might force them to switch; this can be useful as Tentacool's main goal is to get all the opposing Pokemon poisoned by Toxic Spikes. An offensive Rapid Spin set with three attacks and Life Orb could work, but Staryu runs this set better as it has higher Speed and Special Attack. Magic Coat is a good option to bounce back all forms of entry hazards, status moves, and Taunt. Rain Dish and Rain Dance can be used together to give Tentacool some recovery and to boost the power of Tentacool's Water-type STAB moves. Swords Dance is a decent boosting move that can be used alongside Tentacool's physical moves, such as Waterfall and Poison Jab, but its low Attack stat leaves it outclassed by other Water-type Swords Dance users, such as Totodile. Venoshock is a great offensive move alongside Toxic Spikes as it power doubles when an opponent is poisoned. Similarly, Hex can be used to hit spinblocking Ghost-types for super effective damage.
Haze is another great option for Tentacool as it can stop opponents from setting up on it, and also possibly stop a sweep. A simple RestTalk set with Toxic Spikes is a possibility to help Tentacool Toxic stall more efficiently. If you get lucky with confusion hax, Confuse Ray can be very useful in trying to Toxic stall the opponent. Barrier, which increases Tentacool's Defense by two stages, can somewhat make up for its terrible physical bulk. Acid Spray can force switches by halving the opponent's Special Defense. Mirror Coat works well with Tentacool's high Special Defense, but, unfortunately, it is illegal with Rapid Spin. Lastly, Toxic can be used if you want a more reliable way of poisoning the opposing Pokemon.
Checks and Counters
Croagunk is a hard counter to Tentacool thanks to its Dry Skin ability and resistance to Giga Drain; it can also absorb Toxic Spikes and 3HKO or 4HKO Tentacool with Shadow Ball or Dark Pulse. Abra and Smoochum can take one Scald with ease and OHKO Tentacool with STAB Psyshock. Scraggy and Dratini both don't fear Scald's burn chance due to Shed Skin; the latter resists Scald as well. Regardless, they can both set up on Tentacool with Dragon Dance and OHKO it with a +1 Crunch or Outrage, respectively. Chinchou can take Scalds with ease as it resists Water-type moves and is not greatly crippled by burn; it can then threaten Tentacool with super effective STAB moves in Thunderbolt and Volt Switch.
Shroomish is a perfect example of a defensive Pokemon that can counter Tentacool; in addition to resisting Scald and Giga Drain, it benefits from being poisoned thanks to its Poison Heal ability. As Tentacool lacks reliable recovery, Shroomish can slowly wear it down with Giga Drain; however, Shroomish must be wary of Liquid Ooze and Sludge Bomb. Ferroseed's typing and bulk enable it to take Scald and Giga Drain with ease, and with Leech Seed, it can wear down Tentacool very quickly. Other defensive Grass-types, such as Chikorita, can also wall Tentacool if they can avoid Toxic Spikes.
Defensive Misdreavus can counter Tentacool as it can take Scald with ease, block Rapid Spin, burn it with Will-O-Wisp, and wear it down with Shadow Ball. Nasty Plot variants, on the other hand, can set up on Tentacool and 2HKO it with a +2 Shadow Ball. Frillish can wall Tentacool with its Water Absorb ability and spinblock thanks to its Ghost typing, but it has to be wary of Giga Drain. Slowpoke can check Tentacool if it avoids Giga Drain and Toxic Spikes as it resists Scald and has access to STAB Psychic. Natu is another great counter as it can bounce back Toxic Spikes with its Magic Bounce ability; offensive variants can threaten Tentacool with Psyshock as well.
Although it must be wary of a super effective Scald and its burn chance, Drilbur makes a good check as it can outspeed and OHKO Tentacool with STAB Earthquake. Diglett can check Tentacool too by trapping it and OHKOing with STAB Earthquake, but it absolutely cannot switch into either Scald or Giga Drain. In general, any physical attacker that carries a super effective move can muscle through Tentacool's terrible Defense.