That's not necessarily unsafe, but you're also probably not going to catch very many walleye 100 yards offshore. Most fishing for walleye is done miles offshore. If you're up there in may, you should be able to catch plenty of white bass in and around either of the rivers since they will be spawning. As far as walleye from a yak, I'd say again to consider the Sandusky river during April. The water will still be extremely cold, but you'll be a hell of a lot closer to shore.