Why you're not supposed to use an extension cord on a 120v : r/hottub
Amazon.com: GFCI Cord Replacement for Hot Tub, Spa & Pool - 120V/15A Inline Style : Patio, Lawn & Garden
HDX 8 ft. 16/3 Light Duty Indoor Tight Space Extension Cord with Banana Tap, Black HW1638HDBF - The Home Depot
ALEKO 120 Volt 4 - Person 130 - Jet Round Inflatable Hot Tub & Reviews | Wayfair
✓ LifeSmart® Spas Power Cord GFCI Two Buttons, 110V-120V, 15 Amp 15' FT 14/3 Cord, Outdoor Rated Fits the LifeSmart® Spas models with the Plug and Play Power Cord GFCI
Utilitech 40-ft 14 / 3-Prong Outdoor Sjtw Medium Duty General Extension Cord in the Extension Cords department at Lowes.com
Amazon.com: GFCI Cord Replacement for Hot Tub, Spa & Pool - 120V/15A Inline Style : Patio, Lawn & Garden