Sentinel 3 and sentinel 2 fusion

I want to do fuse sentinel 3 and sentinel 2 for marine water application. For checking the fusion method accuracy I’m using the level-1 product of both sensors (MSI and OLCI). I have converted the radiance of s3 to Top of atmosphere reflectance and re-project the data. Should I do any other pre-processing before fusing these images to match the spectral data of S2 and S3?

Probably you need the higher geolocation accuracy for S3.
See here:

Processing time will increase.

Hi, I also want to do some fusion with S2 and S3,.In my opinion, we should get the S3’s Apparent reflectance(TOA->BOA) But I don’t know how to do it?

Currently, there is no way to get the BOA reflectance.

You could apply the Rayleigh Correction. But this is only a part of an AC.
There is only the S3A_OL_2_WFR product from Eumetsat, but this provides only reflectances over water.

Thank you very much!