I haven't run a Sr HT in over 10 years and I remember this rule:
Section 6. Senior Hunting Test. Dogs shall be tested in a minimum of four hunting situations that shall include one land blind, one water blind (that may be run as a double blind on land and water), one double land mark, and one double water mark. There shall be at least one diversion shot and at least one of the hunting situations shall include a walk-up. In Senior tests, a double mark is defined as two marks presented before the dog is sent to retrieve. Blinds shall not be run between marks in Senior Hunting Tests.