Can this be used in a Chlorine pool?

Yes, it is designed for use in chlorinated pools.

Are you supposed to wear anything underneath?

I never wear anything under these when training and they are comfortable. I've been using them for 2 years this way.

Would a 34 to 36” waist be large?

XL FOR SURE !! I'm 6'1 and Weigh 200 lbs. My Waist is 35" Currently. I Ordered XL and They Fit Snug! ☆ Almost TOO Tight!! The 1st Time I Tried them on, The Front was so TIGHT That It Completely Smashed my TOOL!! ☆ But, Part of the Problem was Me Pulling them up as High as I Could! ☆ These Shorts Fit Better if You Let them Hang a Little Bit Low on Your Hips! ☆ FYI, I'm Not Talking about Having the Front Rest just above Your TOOL And/Or Having Butt Cleavage . . . . . ☆ Just Put them on and Find a Good Position on Your Body to Allow them to Be Comfy, While They're Doing Their Job ( Keeping Your Bum Warm & Buoyant )!! ;D

Item Package Dimensions L x W x H	21.34 x 11.02 x 3.15 inches
Package Weight	0.44 Kilograms
Item Dimensions LxWxH	12 x 12 x 2 inches
Brand Name	ROKA
Color	Black/Atomic Red
Material	Neoprene
Suggested Users	mens
Manufacturer	ROKA
Part Number	1011-1181-004-210
Style	Modern
Size	Small
Sport Type	Swimming, Triathlon

ROKA Men's SIM Elite II Neoprene Buoyancy Shorts for Swimming Racing and Triathlon

Description

Specifications

Common Questions