They don't rent ECVs at the water parks, but font prevent people from bringing one in.
There are paved paths, but there are also a lot of sand areas, which are not
ECV accessible (sand is too soft).
This is a link to the Typhoon Lagoon park map, which includes icons that show what the access is.
https://wdpromedia.disney.go.com/me...park-overview/Water-Parks-March-2016-comp.pdf
The majority of attractions are only accessible to guests who are able to walk (the little standing figure)
A few are wheelchair/ECV accessible, but guests need to transfer to the attraction (icon with stick figure getting out of wheelchair).
The ECV symbol with an arrow to a wheelchair means that ECV users need to transfer to a wheelchair.
This clip from the map shows the icon for each attraction.
View attachment 189493