A bottomless pit in Happy Tree Friends Adventures.
A pit, also called an abyss or a bottomless pit, is a common hazard in the Happy Tree Friends Adventures series. This type of hazard has no safe ground to stand on, so if someone (player or enemy) falls down a pit like this, they will die.
Despite this, depending on the level's layout, what appears to be a pit at the end of a level's section is instead the only way forward. In this case, no lives are lost when the player's character falls in this type of pit and they end up in the next section of the level.
Aesthetically, pits can take many forms. Although the tree friends can swim in some games, if the water they end up in covers a bottomless pit and the player lets them sink through it, or they fall into certain bodies of water they can not swim in at all regardless of the presence of proper swimming mechanics, they will lose a life just as if it was a pit. In levels with quicksand, allowing the player's character to sink through it is the same as falling into a pit. Lava is also essentially a pit.