A tension device for securing a floating structure includes an elastic member, first and second end members, and an inelastic member. The elastic member is stretchable under tension from an unstretched length to a stretched length. The first and second end members are carried at first and second ends of the elastic member, respectively. The inelastic member is secured to the first and second end member and limits the stretched length of the elastic member. First and second restrictive apertures are limited in diameter by first and second sewn portions of the inelastic member, respectively. The first and second restrictive apertures prevent separation between the inelastic member and the first and second ends of the elastic member, when the tension device is loaded in tension.