Cloudcape

Wondrous item; uncommon (optional attunement)
  While you wear this cape of shimmering water vapour you can, with a gesture, cause it to billow behind you, creating a glimmering rainbow if you are in bright light. In addition, you have a swimming speed of 30 feet and leave a trail of obvious bubbles in your wake whenever you swim.
  Optional Attunement. If you choose to attune to this cape, it gains the Fog property while you remain attuned to it. This cape has 3 charges, and regains all expended charges daily at dawn.
  OA: Fog. As an action you can expend 1 charge to send the vapour portion of the cloudcape to a point you can see within 120 feet of you where it disperses, casting the fog cloud spell centred on that point. The spell does not require concentration when cast in this way. As a bonus action you can end the spell, causing the fog cloud to disappear and the cape to reappear on your back.
  Rare variant: While you wear this cape you can breathe underwater. Increase the swimming speed to 60 feet and the number of charges to 4. While you are attuned to this cape it gains the Gas property:
  OA: Gas. As an action you can expend 2 charges to cast the gaseous form spell on yourself.
  Very rare variant: While you wear this cape you can breathe underwater and gain a flying speed of 30 feet. Increase the swimming speed to 60 feet and the number of charges to 6. While you are attuned to this cape it gains the Gas and Cloudstride property:
  OA: Cloudstride. As an action you can expend 3 charges to cast the cloudstride spell, requiring no material components.