There are a few places around Mallets Bay in Lake Champlain where you can launch a boat:
Malletts Bay
This access in Colchester has a long wide concrete ramp. There are docks on either side of the ramp and generally three pickup trucks can launch at one time. There is ample parking and It’s open all year, making it an ideal spot for ice fishing and pond hockey in the winter.
https://anrweb.vt.gov/FWD/FW/FishingAccessAreas.aspx?aa=Malletts%20Bay
Amenities: dock, parking, fuel
Colchester Point (Windermere Way)
Another access in Colchester, on the Winooski River with a ramp for small watercraft. It also has parking, and it’s open all year for boating and fishing.
Apple Island Resort Boat Launch (Causeway/Sandbar)
71 US-2, South Hero, VT
This public boat launch is located on the north side of the causeway/sandbar/bridge. There is ample parking and It’s open all year. There is a private marina adjacent to the launch.
Amenities: dock, parking, fuel
These places are all managed by Vermont’s Fish & Wildlife Department