Can Fleet prevent enemy units to cross rivers ?

[ElvisKnowsTheGame]

Hello

I have a question (actually i have many ... )
I understand that a fleet can prevent enemy unit to cross a river, estuary or a strait, right ? But how many ships do you need, and is it 100% reliable ?
Does the fleet also prevent the supply to cross ? (Supply is a nightmare)

[Offworlder]

Yes fleets block land units from crossing from one side to another. Just mouse over the body of water and it will tell you how many ships you need to block that particular body of water. However, you need some sort of warship to do so