Patch it, don't heat it

For a seam split in a pool float, the reliable fix is a vinyl patch applied with a compatible adhesive.

Clean the area around the split with isopropyl alcohol and let it dry completely. Rough it up lightly with sandpaper so the patch actually bites. Apply a vinyl adhesive (like a PVC repair glue) and press a patch over both the seam and a bit of surrounding material. If the split is along a stressed seam, patch both sides for extra holding power.

Don’t reach for super glue — it goes stiff and cracks as the float flexes. And skip heat welding unless you know exactly what you’re doing; you’ll end up with a worse hole. Tapes are a temporary fix at best.

Let the patch cure overnight before inflating. That’s the difference between a fix that lasts and one that fails mid-afternoon.