<![CDATA[ABSTRAKSelat Makassar merupakan jalur strategis antara Kalimantan dan Sulawesi yang menghubungkan Samudera Pasifik dan Samudera Hindia. Selain menjadi rute pelayaran internasional penting, wilayah ini juga rawan terhadap ancaman keamanan seperti ranjau laut dan drone bawah air, sehingga membutuhkan pengawasan ketat dan kerja sama lintas sektor. Penelitian ini bertujuan untuk mengeksplorasi karakteristik kolom air, khususnya lapisan termoklin yang berpotensi menjadi wilayah persembunyian (Shadowzone), pada kedalaman 0–300 meter di choke point Selat Makassar. Data suhu dan salinitas terhadap kedalaman diperoleh dari pengukuran argo float selama periode Oktober 2017 hingga Januari 2018. Perhitungan kecepatan rambat suara dilakukan menggunakan persamaan empiris Medwin. Lapisan termoklin diidentifikasi melalui gradien suhu sebesar 0,1°C per meter. Visualisasi dan analisis data dilakukan menggunakan perangkat lunak ODV 5.6.2. Hasil penelitian menunjukkan bahwa lapisan termoklin berada pada kedalaman 86,4–158,1 meter, dengan suhu 16,79–27,98°C, salinitas 33,75–34,67‰, dan kecepatan suara 1514,19–1541,95 m/s. Ketebalan lapisan sekitar 72 meter ini diindikasikan sebagai Shadowzone yang potensial menjadi lokasi persembunyian objek bawah laut.Kata Kunci: Selat Makassar, Lapisan termoklin, Suhu, Salinitas, Kecepatan SuaraABSTRACTThe Makassar Strait is a strategic route between Kalimantan and Sulawesi that connects the Pacific Ocean and the Indian Ocean. In addition to being an important international shipping route, this area is also prone to security threats such as sea mines and underwater drones, requiring strict surveillance and cross-sector cooperation. This study aims to explore the characteristics of the water column, particularly the thermocline layer that has the potential to become a hiding place (Shadowzone), at a depth of 0–300 metres at the Makassar Strait choke point. Temperature and salinity data at different depths were obtained from argofloat measurements during the period from October 2017 to January 2018. Sound propagation velocity calculations were performed using the Medwin empirical equation. The thermocline layer was identified through a temperature gradient of 0.1°C per metre. Data visualisation and analysis were conducted using ODV 5.6.2 software. The results of the study show that the thermocline layer is located at a depth of 86.4–158.1 metres, with a temperature of 16.79–27.98°C, salinity of 33.75–34.67‰, and sound velocity of 1514.19–1541.95 m/s. The thickness of this layer, approximately 72 metres, is indicated as a potential shadow zone for the hiding of underwater objects.Keywords: Makassar Strait, Thermocline Layer, Temperature, Salinity, Sound Velocity ]]>
