Since the 1970s, artificial reef (AR) deployment has been one of the common approaches to augment the local production of coastal fish in Malaysia. However, there is a lack of strategy to assess and evaluate the success of pre-deployed AR. Realizing the need for an effective qualitative and quantitative monitoring and evaluation of AR, this study proposes side-scan sonar coupled with scuba diving observation for the enhanced monitoring of pre-deployed Bioceramic Korean (BK) AR along the coast of Terengganu, Peninsular Malaysia. This method employs an integrated side-scan sonar with a data acquisition system for the detection of the precise location of the BK AR which were deployed at Tukun Telaga Batin off the Terengganu coastline in 2003 by the Fisheries Development Authority of Malaysia (FDAM). Following the determination of the exact location of three BK AR areas, a scuba diving team was sent to survey the physical conditions of the AR and assess the feasibility of the AR as an artificial habitat for marine life. The scan sonar images were compared with the captured photographs and videos acquired during the scuba diving session for a comprehensive value-added assessment. The collected data from the scuba diving session were also processed to measure the fish diversity, the fish biomass, and identify the fish community surrounding the AR. Based on the results, the BK AR remained in extremely good condition, physically intact, without significant breakage or damage, and with no major subsidence into the sediment after 19 years of deployment. A total of 108 BK AR modules were detected in three large groups using the mosaicked sonar images. Following cross-examination to validate the AR measurements using the AR’s shadows on the seafloor, the height of the BK AR consistently ranged from 1.7 m to 1.8 m. In addition, 34 species of fish from 14 families and 26 genera were identified, with most species classified as reef-associated (RA) fish with a biomass value of 1173.31 ± 1136.69 kg m⁻³, indicating the successfulness of the BK AR as fish-aggregating devices (FADs). The growth of hard corals on top of the bioceramic plate of the AR module further supported the diversified community of marine life surrounding the BK AR. In conclusion, the side-scan sonar coupled with scuba diving observation demonstrates an effective qualitative and quantitative technique for the monitoring and evaluation of pre-deployed AR. This strategy is recommended to be utilized to determine the success of pre-deployment AR.

Sedimentation poses a significant challenge to navigational safety within port areas, including at Kemaman Port, Terengganu, Malaysia. This study characterised seabed morphology and identifies key features, including sediment distribution, submerged objects, and potential hazards that may impact port operations and navigational safety. Side-scan sonar (Klein 3000 dual-frequency system operating at 100 and500 kHz) and Compressed High-intensity Radar Pulse (CHIRP) sub-bottom profiler (EdgeTech Strata Box) were employed to produce detailed seabed maps of the seabed across four survey zones (CN, P, R, CS) encompassing 23 sampling stations with 50 m survey-line spacing with 50 m line spacing. Sediment analyses revealed that the port basin is dominated by silt-clay mixtures (mean D50 = 0.045 mm, 68% mud content), whereas the river mouth was characterised by coarse sand and gravel deposits (mean D50 = 1.2 mm, 12% mud content). Three distinct acoustic facies were identified and showed strong correspondence with sediment grain-size distributions, achieving 87% classification agreement. A total of 37 potential navigational hazards were identified, including five major scour pits adjacent to the breakwater (15 m–45 m in diameter, 2 m–8 m in depth), 18 submerged objects, and four active bedform fields. High-energy bedforms, with ripple wavelengths ranging from 0.8 m to 1.5 m were observed in the navigation channels, indicating active sediment transport processes. CHIRP sub-bottom profiler data revealed three stratigraphic units with surficial sediment accumulation reaching 1.8 m in the port basin, corresponding to a sedimentation rate of approximately 7 cm per year since port construction. The findings provide quantitative baseline data to provide quantitative baseline information to support port management, assist with marine safety initiatives, and inform future dredging strategies and coastal monitoring programmes in the region.