No experience with an immersion suit but used to dive for abalones off the Northern California coast with water temps in the low 50's. I wore a 1/4" full wet suit with a good hood and gloves. After fighting the surge and getting bashed on the rocks I got tired before I got cold. I could do a little over an hour and then had to rest. I also dove in Lake Tahoe in the winter time, water in the low 40's, and could stay in for an hour or so before my hands started to get numb. The wet suit may take a little longer to get into? I guess immersion suit are on the market for a reason?