PURPOSE: To perform duties of an assembly type catamaran as leisure on a lake and an offshore and to perform the duties thereof as a boat for rescue when emergency occurs.

CONSTITUTION: A double-barrel part is fixed on the upper surface of a double- barrel of a left and right boats 1 and 2 by means of a front coupling plate and a rear coupling part 4, and spanning plates 5, 6, and 7 are arranged at the middle thereof. Lateral displacement is prevented from occurring by means of left and right fixed cylinders 8 and 9. In a handrail 11, the handrail 11 is securely inserted in the front coupling plate and the rear coupling plate 4 and a dash plate 10 and water break bands 17 are mounted on the outer periphery of the handrail 11.