(1) A natural guardian as defined in s. 744.301(1), legal custodian, or legal guardian of the person of a minor may designate a competent adult to serve as a surrogate to make health care decisions for the minor. Such designation shall be made by a written document signed by the minor’s principal in the presence of two subscribing adult witnesses. If a minor’s principal is unable to sign the instrument, the principal may, in the presence of witnesses, direct that another person sign the minor’s principal’s name as required by this subsection. An exact copy of the instrument shall be provided to the surrogate. (2) The person designated as surrogate may not act as witness to the execution of the document designating the health care surrogate.
(3) A document designating a health care surrogate may also designate an alternate surrogate; however, such designation must be explicit. The alternate surrogate may assume his or her duties as surrogate if the original surrogate is not willing, able, or reasonably available to perform his or her duties. The minor’s principal’s failure to designate an alternate surrogate does not invalidate the designation.
(4) If neither the designated surrogate or the designated alternate surrogate is willing, able, or reasonably available to make health care decisions for the minor on behalf of the minor’s principal and in accordance with the minor’s principal’s instructions, s. 743.0645(2) shall apply as if no surrogate had been designated. (5) A natural guardian as defined in s. 744.301(1), legal custodian, or legal guardian of the person of a minor may designate a separate surrogate to consent to mental health treatment for the minor. However, unless the document designating the health care surrogate expressly states otherwise, the court shall assume that the health care surrogate authorized to make health care decisions for a minor under this chapter is also the minor’s principal’s choice to make decisions regarding mental health treatment for the minor. (6) Unless the document states a time of termination, the designation shall remain in effect until revoked by the minor’s principal. An otherwise valid designation of a surrogate for a minor shall not be invalid solely because it was made before the birth of the minor.
(7) A written designation of a health care surrogate executed pursuant to this section establishes a rebuttable presumption of clear and convincing evidence of the minor’s principal’s designation of the surrogate and becomes effective pursuant to s. 743.0645(2)(a). 
