Can't say i've ever really tried a true, brilliant citrus aquatic. Many related/close genres, but they are either lacking enough natural citrus to earn the term "citrusy", or are too sweet and fruity to not be called "fruity". I'll
List a few favorites:
Erolfa and maybe Bvlgari Aqva are the best "citrus aromatic oceanic" fragrances I've smelled.
L'Eau Par Kenzo, Amouage Cirrus, and Bvlgari Aqva Marine are the best "chlorine aquatics", cannot really consider them citrus or oceanic, as they have no natural citrus, and their watery/aquayic accords smell more like indoor pools than real oceans or seas.
The best "laundry aquatics" I feel are both Eau De Cartiers, and Mattiolo Uomo.
The best "sandy aquatic", which also has a laundry nuance to it, is Amouage Ciel Man.
The best "fruity citrus aquatics" are Millesime Imperial, Unforgivable Multi Platinum, Bond Wall Street, and Amouage Arcus.
The best "citrusy green-floral aquatics" IMO are Silver Mountain Water, Xerjoff Mefisto, and Kilian's Prelude to Love.
And some fresh citrusy scents (not necessarily aquatic but super fresh and modern, are either Hermes D'Orange Verte, Truefitt & Hill West Indian Limes, Penhaligon's EDC (yes it's modern). I'd recommend Selection Verte, some Nicolais, and Maitre Pour Le Jeune Homme, but those might not be quite modern enough for you, even though I feel they're timeless.