Abyssal Strike

The next time you hit a creature with a melee weapon attack during the spell's duration, your weapon glistens with bubbles and steam, and the attack deals an extra 1d6 cold damage to the target and causes them to be surrounded by tumultuous water. Until the spell ends, the target is considered to be inside difficult terrain and cannot speak.

At the start of each of its turns the target can make a Dexterity saving throw, escaping the water and ending the spell on a success

At Higher Levels: once you cast this spell using a spell slot of 2nd level or higher, the additional damage increases by 1d6 for every level above 1st.