Anyone Familiar With Wetsuit Type Material?

I'm looking for some rashguard type shorts to wear under my boardshorts. I found some I think I like, but they mention something in the description about keeping you warm in chilly water. The fabric is 6 oz. nylon/spandex. Does anyone know how thick that is in terms of how much heat that's going to hold in? I'm wanting them for the beach and the summer so I don't want something that is going to make me uncomfortably hot. Any help is much appreciated!

 

Surf in Louisiana???

 

Thanks! That's exactly what I needed to know

Haha and no, no surf in Louisiana, but there is wakeboarding and we make trips to the beach pretty often

 

X La. boy here Grew up in Shreveport moved down here in 1963.