Creatures engulfed by a Watery Sphere are restrained, which grants advantage on all attacks against them. However, they may also be considered underwater, which would impose disadvantage on most ranged weapon attacks and negate the advantage. Does attacking into the sphere with a ranged weapon have advantage, or do the underwater combat rules apply to this situation and negate that advantage? (Assume the ranged weapon is not a crossbow or one of the other weapons that doesn't suffer disadvantage underwater.)
RAW is unclear
The Underwater Combat rules on page 198 of the Player's Handbook are very short and don't give a great ruling on what counts as underwater combat. They state:
Underwater the following rules apply. [...]
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...
These rules seem to assume that all both the attacker and the target are underwater. They also assume the line of attack is underwater for it's entire length.
In the case of watery sphere nowhere in its description does it mention whether or not the target is considered underwater. As spell's only do what they say they do you could argue that this means they are not underwater. This doesn't agree with a logic interpretation of the spell however.
On a failed save, a creature is restrained by the sphere and is engulfed by the water.
I said in an related answer that I consider "engulfed by the water" to be equivalent to being underwater for the purpose of drowning. The same ruling should apply here, although it is open to DM interpretation.
As there is no exact ruling to cover the condition where a creature is firing into water the only correct answer is "up to your DM".
How I would rule it
Here is how I see it and would rule as a DM however.
Ranged weapon attacks miss beyond their normal range due to the drag of the water. If the attack is in the air for the majority of its flight and only enters the water immediately before striking the target this restriction doesn't make sense. The same reasoning apply for why ranged attacks have disadvantage underwater.
With this logic I can see three possible logical rulings:
- An attack uses the underwater combat rules if the attacker is underwater
- An attack uses the underwater combat rules if more than half its range in underwater
- An attack uses the underwater combat rules if more X feet of its path are underwater.
Of the first two, I am not convinced either way which is a better rule and have played with both. This situation is rare enough that it has only come up once or twice with each rule and I haven't noticed a major difference. I have never used the third rule but may implement it the next time this situation comes up.
In the situation of watery sphere all the rules would mean that the attack is made with advantage in most cases. The attacker in not underwater and the attack in not underwater for more than half its range, therefore underwater combat rules do not apply. There is a slight chance that if you are adjacent to the sphere and attacking through it against a creature trapped 10ft from you that more than half of the distance is underwater, but this is an edge case.
In summary I would rule: The attack has advantage because the attacker in not underwater and the majority of the range of the attack is not made underwater.