Spa shell reinforcement systems and methods

A reinforcing system for a vessel that can contain water, the system comprising:

• a thermoplastic shell for containing water, the shell having at least one jet predetermined location on at least one sidewall of an underside of the shell;
• and
• a structural support layer on the underside of the shell, the structural support layer comprising:
• an inner layer of rigidizer that is 0.2 centimeters to 1 centimeter thick, the inner layer comprising a layer of polyurethane;
• a foam support layer that is 0.5 centimeters to 3 centimeters thick;
• and
• an outer layer of rigidizer that is 0.25 centimeters to 1 centimeter thick,
• wherein the structural support layer extends from a bottom side of the underside of the shell, across the at least one sidewall of the underside of the shell, to a lip of the spa shell, the structural support layer forming at least one rib along the sidewall of the underside of the shell.