Hydro Freeze

When a wet creature recieves damage from a spell that deals cold damage, they must make a Strength saving throw against a DC equal to 10 + the slot level used. On a failed save, they become frozen until the start of the caster's next turn.

Additionally, when a spell that deals cold damage reaches a surface of water, the following can happen:

• If the spell is a projectile that targets only one creature, such as Icicle Break, it explodes when it hits the water freezing a 5-foot radius circle on the surface of the water, with 10-foot long spikes growing underneath. If you cast the spell underwater, the spell becomes a 15-foot cone of ice spikes.
• If the spell targets an area, such as Icicle Field, it stops when it hits the surface of the water and creates spikes of ice for double the area underneath the water. All creatures on the area must make a Dexterity saving throw. On a sucess, they are affected by all the effects of the spell. On a failed save, they take half the damage. If the spell targets a point underwater, it becomes a sphere of ice spikes.
• If you conjure a structure of ice on a point, such as Ice Pillar, and use it underwater, it becomes a sphere of ice spikes with a radius equal to the spell's highest dimension.

Creatures within range of the spikes must make a Dexterity saving throw. On a success, they are affected by all the effects of the spell. On a failed save, they take half the damage.