If your are looking for an aprtment in the beach of Valencia city, thers'nt too much offer.
Pinedo, almost attached to Valencia the new seaside walk have been renewed and there are some good restaurants, but no stores and not touristic, the beach is the worst of the province, close to the seaport. The nearest stores are at valencia city and you need to use the car or take a local bus, walking to the city is not a choice.
Best Valencia city beach is Malvarrosa in the other side of the seaport but it's much better than Pinedo, but there isn't many apartments to rent as in any touristic town in the coast. It looks more urban. There are some hotels though and the center is much more closer, buses and tram available. Not a very commercial zone.
El Saler, some typical towers of apartments, easier to find there something for rent, beaches are quite good, but it's a bit far from the city (despite it belongs to valencia city). Good environment, calm, offer of resturants at El saler town.
Consider also Alboraya seaside urbanizations, probably some apartments there, the same beach of Malvarrosa (the town of Alboraya is a bit inland).
Buses to the center of Valencia.
PortSaplaya, very very touristic place with beach, as far as El Saler to the center of valencia, probably woest connections with public transport (i think this place belongs to Alboraya).