This non-provisional application is a continuation-in-part application filed under 37 CFR 1.53(b) that claims the benefit of United States 35 USC 120 from non-provisional application U.S. Ser. No. 16/174,357 filed on Oct. 30, 2018, by the inventor: Danny Street. The sidewall-suspended boat cooler replaces the U-shaped space of the prior disclosure with a telescopic hook. Specifically, the rear wall overhang extension is removed and replaced by the telescopic hook. The telescopic hook catches on the sidewall of the vessel such that the telescopic hook combines with both: a) the superior horizontal surface of the prior disclosure; and, b) the vertical transfer surface of the prior disclosure to form a mechanical U-shaped structure in which the sidewall of the vessel inserts. The form factor of the telescopic structure is adjustable such that the mechanical U-shaped structure can adjust to accommodate variations in the form factor of the sidewall of the vessel.