Your rash guard should fit like a second skin.

Yes, it should be snug — not loose, not painted-on tight. No baggy fabric anywhere.

The main problems with a loose rash guard are chafing (constant rubbing from the suit or board) and water drag. Surfing is already hard enough without extra resistance. A snug fit keeps the fabric against your skin, reducing friction and staying tucked in your wetsuit or board shorts.

Look for 4-way stretch nylon/spandex blends. Don’t go by your t-shirt size — check the brand’s size chart and measure your chest and torso length. If you’re between sizes, size down. You want it to move with you, not hang off you.

A rash guard that fits well won’t ride up when you paddle. That’s the real test.