Overwhelm. To epipelagic merfolk moving, hunting, and fighting together comes naturally. When an ally within 5 feet of you misses with an attack you can use your reaction to make an attack against the same target with either an unarmed strike, a weapon, or a cantrip with a casting time of 1 action and must target only that creature. You can make an attack in the way a number of times equal to your proficiency bonus per long rest.

Communal Movement. After you take the dash or disengage action any ally you move within 5 feet of can use their reaction to move up to their speed to follow you. They must end their movement within 5 feet of a space you were after they started following. Attacks against them during this movement are with disadvantage.
After an ally that took the dash or disengage action moves within 5 feet of you you can use your reaction to move up to your speed to follow them. You must end your movement within 5 feet of a space they were in after you started following. Attacks against you during this movement are with disadvantage.

Confidnent Roamers. Epipelagic merfolk confidantly and swiftly move between places, be it hunting grounds, gathering areas, or anything else. You don't suffer any disadvantages from moving at fast travel pace like disadvantage on perception checks.