shark
鮫 centers on the shark, a large predatory fish. The meaning is straightforward and specific to this animal.
鮫 combines 魚 (fish) with 交, which likely contributes the sound. The character was created to specifically denote a shark.
The left side is a fish 魚, and the right side 交 looks like a cross or intersection. Imagine a shark's fin cutting through the water like a crossing blade: a fish with a crossing fin is a shark.
For コウ, picture a shark swimming in a cove: cove -> コウ, and the shark glides through the cove's water.
shark
sturgeon (esp. the green sturgeon, Acipenser medirostris)
remora (any fish of family Echeneidae); suckerfish; sharksucker
great white shark; white pointer (Carcharodon carcharias)
swellshark (Cephaloscyllium ventriosum, species of catshark in the Eastern Pacific)
winghead shark (Eusphyra blochii, species of Indo-West Pacific hammerhead shark)
horn shark (Heterodontus francisci, bullhead shark from the Eastern Pacific); Californian bullhead shark
kaluga (Huso dauricus); river beluga
Caribbean reef shark (Carcharhinus perezii, species of requiem shark found in the tropical waters of the western Atlantic Ocean from Florida to Brazil)
blotchy swell shark (Cephaloscyllium umbratile)
salamander shark (Parmaturus pilosus)
yellow guitarfish (Rhinobatos schlegelii)
whitecheek shark (Carcharhinus dussumieri)
sterlet (Acipenser ruthenus)
bull shark (Carcharhinus leucas)
beluga (species of sturgeon, Huso huso)
nurse shark (Ginglymostoma cirratum)
sterlet (Acipenser ruthenus)
Asian brown flycatcher (Muscicapa dauurica)
thresher shark (esp. the common thresher shark, Alopias vulpinus)