If the  correct pretreatment ...

If the  correct pretreatment is selected then  a RO plant should be able to operate in a reliable manner with all seawater sources.  The pretreatment may require several process  steps depending on the level of none salt material in the source seawater.  

If the source seawater has high suspended solids/ turbidity  sand or silt from rivers, then a lamella clarifiers process step are often used (eg Trinidad Point Lisas). 

If the source seawater has high algae or oils and grease then Dissolved air Floatation is typically used (eg Fujairah) .  Dual Media Filters  are used for low levels of the turbidity (typically up to 10 NTU) (used on most desal plants) , and also a very deep pumice top layer is now often used in the DMF as  biofilter  to remove organic material that could other wise cause biofouling to the RO.  

If there is  industrial organic pollution then another step is the granular active carbon filters.  (eg Carboneras Spain).  UF/MF membrane pretreatment although very good for particulate material is not effective for soluble material and tends to lead to biofouling of the RO membranes if there is no biofilter process added also to the pretreatment train.