Jet boats were once mostly hairpin-­happy thrill rides, with the reflexes of a slot-car. Today, they’ve matured into hot-selling family models, viable alternatives to craft propelled by propellers.

Highfield’s Velox 420 is a ­welcome addition to the entry-level-­­boat segment. Priced at $36,000, this jet-powered RIB is intended to fill the compact runabout niche somewhat abandoned by popular ...