Heading to Maui in mid August.
Is there a certain time of day to see more wildlife? Thank you

Aloha! I don't think there's a best overall time of day. It really depends on the tides, feeding times, weather, etc. I would be a little more concerned about the water conditions than the time. Swells can change rapidly in Hawaii, so just make sure there are no advisories. I find snorkeling the most enjoyable when it's warm, sunny and calm waters. Also, I believe some places offer full-moon dives and snorkel tours. It's not necessarily better, but is a little more exciting and you're more likely to see entirely different kinds of wildlife. No matter what time you go you're bound to see beautiful fish. Especially if you've never snorkeled in tropical waters before. Have fun!