REDU format ruling
Water Hazard

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Once per turn: You can Special Summon 1 Level 4 or lower WATER monster from your hand. You must control no monsters to activate and to resolve this effect.
Rulings
- The effect to Special Summon a monster starts a Chain.
- If the effect of "Water Hazard" activates, and an effect is Chained that gives you to control of a monster, the effect of "Water Hazard" will not be applied.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.