A portable spa comprises a reservoir for holding water and an outer wall spaced outwardly from the reservoir. The invention makes use of the fact that in MOS devices the threshold voltage is proportionally correlated to the oxide thickness of said MOS device. The disclosed systems may be used to monitor up to sixty-four meters per system, wherein each of the sixty-four meters is monitored at least once per second. The decorative body can be designed to represent animate or inanimate objects, or characters. Heated gas such as nitrogen or dry air is injected into the sleeve to prevent scrubbing liquid from condensing within the sleeve and thus inhibit particulate deposition therein. For expanding the hole, a dilator region is provided between the distal end of the guidewire body and the distal portion for expanding the hole, and has a tapered profile.