The doctor says there's nothing wrong with my eyes. but are these ocean-like waves signs of retina detachment?

Probably vitreous: Apparently you have seen an eye doctor already, but sometimes a second opinion can help. The visual sensation of ocean-like waves is usually from movement of the vitreous in the eye, which has a wave-like motion. The vitreous liquefies usually between age 50-70, and some people become aware of this. Floaters and flashing can also occur. The retina is usually healthy, but should be monitored.