Does using a crossbow with the Sharpshooter feat change its range in underwater combat?

Question

The "Underwater Combat" section of the Combat chapter (PHB, p. 198) reads:

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).

The Sharpshooter feat (PHB, p. 170) reads:

Attacking at long range doesn't impose disadvantage on your ranged weapon attack rolls.

With both of those in mind, would a PC with a Hand Crossbow and the Sharpshooter feat be able to shoot further than 30 feet underwater?

Answer 1

No: the maximum range is reduced.

The benefit is that the attack is not at disadvantage; you get that benefit from using a crossbow underwater.

This is one of those cases where the rules and verisimilitude tend to match up. The sharpshooter feat can't remove disadvantage if the attack automatically misses. There isn't even an attack roll to make if there's no chance to hit.
(If you take a page from PHB Chapter 7, the dice are only rolled when the outcome is in doubt). What the Sharpshooter feat offers is a removal of disadvantage for long range when there is a chance, however large or small, to hit.

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). (Basic Rules, Ch 9; Underwater Combat ; bolded for emphasis)

From the Weapon Table:

Crossbow, hand 75 gp 1d6 piercing 3 lb. Ammunition (range 30/120), light, loading

Answer 2

Sharpshooter doesn't counter underwater combat rules.

As you said, Sharpshooter remove the disadvantage if you attack within your weapon's long range. However, the underwater combat rules state that :

A ranged weapon attack automatically misses a target beyond the weapon's normal range.

It's not a disadvantage, the attack just miss. Sharpshooter doesn't interact with auto-miss. If you want a logical reason, imagine that the shot isn't more difficult to aim but the density of the water slowing down the ammunition remove any possibility of damage beyond a certain range.

As a note, if your weapon wasn't one of the specified type, you would also have disadvantage in the normal range since Sharpshooter only remove disadvantage caused by attacking with the weapon's long range.