My party recently tipped over a boat of enemies into what was essentially rapids and trapped the enemies in a cube of force underwater. The warriors inevitably drowned as they had no way out. However, trapped in the cube of force was a wizard with access to a teleportation spell (Misty Step) with a verbal component. Could the wizard use his spell with a verbal component underwater and escape a watery death? If the rules don’t specify anything about verbal components underwater specifically, have any of the designers mentioned anything about this?
Note: as a 5e DM I made a ruling on the spot (decided to allow it on the condition that the caster goes directly from “holding breath” to “suffocating”) so I am aware that it’s within my power to decide how it works in my world. I’d just like to know if the rules or someone wiser than me has addressed this yet.