We went a two-filter route because we encountered many places where the water was extremely silty. If that silt got into the tank it would settle to the bottom, and some day after several tanks fills we would be pumping mud through our expensive charcoal filter and clog it up.
The first filter was a silt and sediment filter that was attached to the dock hose and filtered the water as we filled the tank. With clean, perhaps still smelly water, we ran the tank water through a 1 micron undersink charcoal filter. The 1 micron effectively filtered out parasitic cysts such as cryptosporidia and giardia that chlorine and iodine don't kill. These nasty cysts aren't just in Caribbean water supplies, but put Sydney, Australia into a tizzy when their water supply was contaminated and the entire city was instructed to boil their drinking water!
We bought these water filters in many places, including Ace Hardware in Malaysia. They're tough, but they don't like being dropped ten feet onto concrete (dropped it a time or two when we were on the hard).
The filters don't really increase the pressure significantly, so you could use them with a manual freshwater system. When not at a dock we would siphon our jerry-jugged water through the silt-only filter into the tank, and the speed of filling was limited by the size of the hose.
Here's a picture of the filter, showing just how much sediment there was in just one 75-gallon tank fill!