The present disclosure provides systems, apparatuses, and methods for measuring submerged surfaces. Embodiments include a measurement apparatus including a main frame, a source positioned outside a pipe and connected to the main frame, and a detector positioned outside the pipe at a location diametrically opposite the source and connected to the main frame. The source may transmit a first amount of radiation. The detector may receive a second amount of radiation, determine a composition of the pipe based on the first and second amounts of radiation, and send at least one measurement signal. A control canister positioned on the main frame or on a remotely operated vehicle (ROV) attached to the apparatus may receive the at least one measurement signal from the detector and convey the at least one measurement signal to software located topside.