Edison format ruling
Water Hazard

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 Edison forum — sourced change requests get reviewed.