Just had my 350Z detailed. The next day it rained and i got a lot of water spots. It also had a sealant coat. Should this be enough to prevent water spots? They almost look like there etched in after the first rain.

 

keep a shamwow handy. wipe off car when it gets wet. no spots.
otherwise, spots in perpituity.

 

Typically if you have a good coat of protection the moisture should roll off with ease. It will also help if the paint has been freshly polished and clayed so it's even smoother underneath the sealant. It's unlikely that the water would etch through with a fresh coat of sealant but it is possible. If it was really hard water and there was enough sun/high temps it could happen.

Greg @ Detailed Image

 

if you still have water spots on your car, i would suggest chemical guys water spot remover. it worked for me. i bought if from detailed image.

 

seems weird that you would get water spots after a good detail. after i detail my z, rain water just rolls off and leaves no trace. if you continue to experience the problem, i'd give CG Water Spot Remover a try.