[Pyros]

2) There are tricks to make the job considerably less in the creation of such a map.
For example you should modify the range of the fill map function to a desirable value (10?) and then you may design your map by right clicking on the water locations (after selecting the water map tool). This way you will design in no time the sea part of your map. After you finish this job, you will have to refine the shores.
The only point to pay attention is that you should make this map a beach assault map before you deploy the assaulting forces. Also you should always put those forces in a direct path with the landing location. If you make an island (surrounded by water) and you put an assaulting unit in the upper edge of the map, then this unit will simply travel up to the left edge of the map without disembarking in the island location.
There are at least a dozen more techniques to help you work/simulate effects in design of a beach assaulting scenario.
3) 1-3 hexes for nigth conditions (depending the moon, clouds and weather). Also you should modify this value if your map is a city/village map (10+ hexes)

p.s In the sea or in the desert with moon & no clouds conditions your visibility is remarkably high 10+ hexes(I know by experience!)

cheers,