The rules for the Petrified condition are as follows (source):
- A petrified creature is transformed, along with any nonmagical object it is wearing or carrying, into a solid inanimate substance (usually stone). Its weight increases by a factor of ten, and it ceases aging.
- The creature is incapacitated (see the condition), can't move or speak, and is unaware of its surroundings.
- Attack rolls against the creature have advantage.
- The creature automatically fails Strength and Dexterity saving throws.
- The creature has resistance to all damage.
- The creature is immune to poison and disease, although a poison or disease already in its system is suspended, not neutralized.
The rules for drowning are as follows (source)
A creature can hold its breath for a number of minutes equal to 1 + its Constitution modifier (minimum of 30 seconds).
When a creature runs out of breath or is choking, it can survive for a number of rounds equal to its Constitution modifier (minimum of 1 round). At the start of its next turn, it drops to 0 hit points and is dying, and it can't regain hit points or be stabilized until it can breathe again.
For example, a creature with a Constitution of 14 can hold its breath for 3 minutes. If it starts suffocating, it has 2 rounds to reach air before it drops to 0 hit points.
RAW, I see no indication that anything in the petrified condition does anything to the rules for drowning. Thus, RAW, I would argue that a character can drown while petrified, and die from it. However, this does not seem to be RAI (given that you cease aging and become immune to poison and disease), and this is also not how I would personally rule it at my table (especially if a player became petrified, which ime is more common than an enemy).
Note also that Greater Restoration requires that the target be a creature, which, RAW, a corpse is an object, not a creature, so it would be impossible to cure the petrified condition of a creature who has drowned with this spell (RAW, you would need to use True Resurrection or Wish to cure the petrified condition from someone who drowned while petrified). Again, this isn't how I would personally rule it at my table, but that's what RAW says.