O "Combate subaquático" A seção do capítulo Combate (PHB, p. 198) diz:
A ranged weapon attack automatically misses a target beyond the weapon's normal range. Even against a target within normal range, the attack roll has disadvantage unless the weapon is a crossbow, a net, or a weapon that is thrown like a javelin (including a spear, trident, or dart).
O Bom atirador feat (PHB, p. 170) diz:
Attacking at long range doesn't impose disadvantage on your ranged weapon attack rolls.
Com isso em mente, um PC com uma besta de mão e o talento Sharpshooter seria capaz de disparar além dos pés da 30 debaixo d'água?