Fossil is a set in the Base series. It was released on 10 October 1999. The printed size is 62, and the checklist is the same length. Tentacool is 56/62, in position 56 of 62 on this checklist. Before it is 55 Slowpoke, and after it is 57 Zubat. The listed rarity is Common.
Tentacool is a Basic Water Pokémon with 30 HP. The card lists level 10. In the Pokédex this is Tentacool (#072), generation 1 (Kanto). The card lists Tentacruel, Tentacruel (#073) under evolves to.
Kagemaru Himeno illustrated this card. The same name is on 656 other cards in the catalog.
Tentacool (#072) has 15 other cards in the catalog. Those other cards are in 13 sets. The other printings with a release date run from 2000 to 2023. The earliest other card is Misty's Tentacool 32/132 in Gym Heroes (2000). That card is named Misty's Tentacool, while this one is Tentacool. That card lists 40 HP, and this one lists 30 HP. The rarity there is Rare, and here it is Common. Ken Sugimori illustrated that card, and Kagemaru Himeno illustrated this one. 14 other cards of Tentacool list a different HP.
Cowardice is listed as Pokémon Power. At any time during your turn (before your attack), you may return Tentacool to your hand. (Discard all cards attached to Tentacool.) This power can't be used the turn you put Tentacool into play or if Tentacool is Asleep, Confused, or Paralyzed. The attack Acid lists 10 damage. The cost is Water. Weakness is Lightning ×2. The flavor text reads "Drifts in shallow seas. Anglers who hook them by accident are often punished by its stinging acid."
I keep a set binder for Fossil, meant to hold every card of that set. This card is one slot in the Fossil set binder. A generation binder holds one card of each species. Tentacool can fill a slot in Generation 1 binder (Kanto). I still need this card.