(01:03:34) Biderp: Start of turn 7 (01:03:34) Biderp: Imber used Water Spout! (01:03:34) Biderp: The foe's Cleffa lost 91% of its health! (01:03:34) Biderp: The foe's Cleffa hung on using its focus sash! (01:03:34) Biderp: The foe's Cleffa used Endeavor! (01:03:34) Biderp: Imber lost 341 HP! (99% of its health) (01:03:34) Biderp: Rain continues to fall! (01:03:34) Biderp: Start of turn 8 (01:03:34) Biderp: Imber used Water Spout! (01:03:34) Biderp: The foe's Cleffa used Toxic! (01:03:34) Biderp: Imber was badly poisoned! (01:03:34) Biderp: Rain continues to fall! (01:03:34) Biderp: Imber is hurt by poison! (01:03:34) Biderp: Imber fainted! (01:03:34) Biderp: Biderp: wat (01:03:34) Biderp: Humpy Thrashabout: you missed? (01:03:34) Biderp: Biderp: its 100 accuracy (01:03:34) Biderp: Humpy Thrashabout: dunno (01:03:34) Biderp: Biderp: well theres a bug apparently water spout missed
I think it's because according to the Water Spout base power formula, it does less than 1 base power. Maybe it's accidentally floored here. I don't know how this base power formula works tbh.
The formula for the power is 150 * Current HP / Max HP. Smogon is usually good for finding detailed info on Pokemon mechanics.
http://pokemon.wikia.com/wiki/Water_Spout <<< Well it seems to suggest here that minimum base power is 10. I haven't been able to find it on a reliable site yet. Edit: Most other sites are just saying a base power of 1 though.