You don't need fresh water in the sea, you need it on shore.
The cost of maintaining anything in the sea is orders of magnitude above that on shore.
A cubic meter of fresh water costs about 3-4 kWh, desal plants are rather compact unlike the solar to power them and land tends to be expensive near shores so it makes no sense to combine solar and desal on the same site.
A cubic meter of fresh water costs about 3-4 kWh, desal plants are rather compact unlike the solar to power them and land tends to be expensive near shores so it makes no sense to combine solar and desal on the same site.