Deep water material question for ROV or DIVE Tech

I am looking for information on a material, solid substance, or product that will be pliable at Sea Level but will become more dense and/or rigid up to a depth of 7,500ft. It would not be necessary for it to become pliable again when returning to the surfaace after being submerged. Thank You for your Time.

[B]??? for ROV or DIVE Tech.[/B]

Looking for a type of Rope or Strap that is flexible at sea-level, that will become rigid at deepwater depths. It would not be necessary for it to become pliable again when returning to the surface after being submerged. Thanks.