Doctor Who: 9 Ways To Kill The Doctor Permanently

Just like us weak and frail little humans, there are certain environments that Time Lords simply cannot survive in.

While the Doctor can survive in space (seen in The Doctor, The Widow And The Wardrobe) as well as the blistering heat of the desert (seen in Planet Of The Dead), one place that will straight-up kill them is if they're completely submerged in water.

There's a clear example of this in Series 4, with the entire premise of the Turn Left episode revolving around an alternate timeline in which the Tenth Doctor is drowned by water from the River Thames. We see his corpse strapped to a hospital bed, while a nearby soldier solemnly declares that "the Doctor is dead."

And this makes sense. When he was drowning, it's not like he had a fatal injury to heal (like a stab wound) that his regeneration could save him from. Maybe he could've tried to regenerate... but then he would still be drowning during his regeneration.

Decades prior to Turn Left, the Fourth Doctor was nearly drowned in classic serial The Deadly Assassin, and on the whole, it seems like Time Lords and large bodies of water should not mix. Hey Doctor - best stay away from that TARDIS swimming pool.