Dreizack - Neptune's weapon has three active forms. The first is a gun, with channels and creates electrical energy in the barrel. The gun is capable of firing quick shots of said energy, or charging for a larger blast. The second form is a guandao, with the blade at the end of the staff lighting up blue and still retaining electrical energy. The third and final active form is a trident, used mostly as a conductor when striking and pinning an enemy and sending an electrical surge through the target.
Water Adaptation - Neptune's semblance works in a few ways. It can enable him to walk on water, with the liquid gaining more substance below his feet, and it also gives him an innate swimming ability so he has never had to learn how. The last manifestation is the ability to breath underwater. However, all but the last require him to have stable emotions and to not be panicking. A difficult feat when one is afraid of the water...