Last time we dove in Maui (early April last year) the water was 74 degrees. I wore a 3mil shorty, my husband wore a 3mil full suit, and another guy on our boat wore a 5mil full suit with a 3mil vest over the top, and complained it was cold. Now for a little perspective....he was from South Florida and only dove when the water was 80 degrees or better, so for him 74 was like an icebox.
We're heading back to Maui this summer, and although the water will be much warmer (should be 80 or so), we'll both wear our 3mil full suits for warmth and critter protection. Depending on your tolerance for cold, either a 3mil full suit or a shorty would be appropriate.
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