What is the name of the bay located midway between the Niagara and St. Lawrence rivers and 3.5 miles east of the Genesee River?

Irondequoit Bay is indeed the correct answer because it is geographically situated between the Niagara and St. Lawrence rivers, as well as being located approximately 3.5 miles east of the Genesee River. This specific location makes it a notable feature on the shoreline of Lake Ontario. Irondequoit Bay serves as an essential waterway, providing access for recreational boating and fishing, and it is recognized for its scenic views and ecological significance.

The other locations listed do not have the same geographical relevance: Lakeview Bay does not exist as a recognized bay in that vicinity; Seneca Bay is not located in the specified area; and Ontario Bay is not a distinct geographical feature recognized within that context. Understanding the significance and specifics of Irondequoit Bay helps in identifying it accurately in relation to nearby rivers and landmarks.