See also comments on Wetsuits page about built-in liners (but there are many wetsuit users who do like such liners)

• Discussion
  • Whatcom Paddlers 1/15/2019
• Stores/Brands the majority of major wetsuit brands and retail wetsuit outlets offer rashguards, but you don't necessarily need to rely on such purpose built options. Many well sewn synthetic shirts, and long bottoms or running tights without prominent seams or labels that might otherwise rub or chaff can serve well as rashguards. Clothing that you have acquired for sun protection likewise may serve as a rashguard if you find it is smooth and does not cause irritation when worn under wetsuits.
  • JLRowing
  • Wetsuit Wearhouse
• …