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For the Gulf it should be fine. If you can handle 68* spring water in a 3mm you should be fine. I'd be frezzing.
mrjimbo has a question.......will my 3mil(I also have "natural" insulation) wetsuit suffice this time o' year, for the spring/and/or/ gulf dive? if so, I'll get a spot for the trailer and come diven if y'all have me!
But some folks like Bugman, etc, wear the 3mm just fine in the springs and don't get cold.