I think being trapped on an overcrowded ship, bodies pressed into you, as the ship capsizes, is also viscerally terrifying. You don't know where you are. You don't know who is around you. You have nothing except what you could've carried. You are trying to leave a downed ship with hundreds of pressing bodies. The waters are rising. There's too much froth to see where you're going.

Everyone is screaming, death is all around you. People are drowning, and in their drowning flailing limbs they are pulling others to their deaths.

[Edited to add: The migrants would've had time to process what was happening to them. There would be many long minutes of terror, suffocation, as they died. Hundreds. Women, children.]