These are the best macro lenses for underwater photography when you want tack-sharp eyes, patterned nudibranchs, shrimp in anemones, pygmy seahorses, crab claws, and tiny textures—shot through flat ports with clean backgrounds and minimal backscatter—and here’s what to look for as you buy: prioritize reliable AF with a limiter (less hunting in dim water), longer working distance (90–105mm FF; 60mm on APS-C/MFT for easier acquisition), flat-field optics with low LoCA so speculars on shells don’t fringe, rounded blades for smooth water-bokeh, and housings/ports that support focus gears and wet diopters; stabilization helps framing but strobes and technique freeze motion, and remember a flat port boosts apparent magnification (~1.33×) while trimming FOV, which is great for macro but demands precise aim. Full-frame dive heroes: Sony FE 90mm ƒ2.8 Macro G OSS (the underwater standard—great working distance and AF), Canon RF 100mm ƒ2.8L Macro IS USM (1.4× topside, excellent underwater detail; limiter is key), Canon EF 100mm ƒ2.8L IS USM (classic in countless housings), Nikon Z MC 105mm ƒ2.8 VR S (crisp, calm color, popular in Z housings), Sigma 105mm ƒ2.8 DG DN Macro Art (mirrorless-optimized, widely supported), plus shorter options for fish portraits and larger critters in lower viz like Nikon AF-S 60mm ƒ2.8G Micro and Canon EF 100mm non-L (budget-friendly, proven). APS-C standouts: Canon EF-S 60mm ƒ2.8 Macro (beloved “first macro” underwater), Nikon AF-S 60mm ƒ2.8G (DX staple), Sony FE 50mm ƒ2.8 Macro on a6000-series (short-tele FOV in water; add wet diopter for super-macro), and the Tokina 100mm ƒ2.8 (via adapters where supported); for Fujifilm X, the XF 80mm ƒ2.8 Macro WR is the go-to in supported housings. Micro Four Thirds stars: Olympus/OM SYSTEM M.Zuiko 60mm ƒ2.8 Macro (the MFT macro king—fast, compact, widely geared), OM SYSTEM 90mm ƒ3.5 Macro IS PRO (2:1 native topside, astonishing with wet optics), Panasonic Leica 45mm ƒ2.8 Macro-Elmarit OIS (great handling in tight spaces), and Panasonic 30mm ƒ2.8 Macro (ultra-close for larger subjects and CFWA-style details). Practical buyer tips: pick ~100–105mm on full frame (or 90mm MFT) for skittish subjects and to keep strobes/you off the reef; choose ~60mm (FF/APS-C/MFT equivalents) for cooperative fish, frogfish, and when viz is mediocre—easier subject acquisition and less AF hunting; ensure your housing supports a flat macro port, focus/zoom gears, and high-quality wet diopters (Nauticam SMC/CMC, SubSee +5/+10, Saga +10) which transform a 60/100 into a super-macro rig; add a snoot (Retra LSD, Backscatter OS-1) for dramatic spot light and black backgrounds; buoyancy arms matter—macro rigs get front-heavy with glass; if you shoot both macro and video, pick lenses with quiet AF and use a red focus light mode to avoid spooking critters. Underwater macro shooting tips: run manual exposure with base ISO (100–200), 1/160–1/250s for strobe sync, and ƒ8–ƒ16 (ƒ11–ƒ22 on smaller sensors when you need depth—mind diffraction); angle strobes outward and slightly behind the port to cut backscatter, or snoot one strobe for inky backgrounds; use a constant focus light low and off-axis, then kill it during exposure if needed; set the AF limiter and use AF-ON, “rock” your whole rig to land the plane of focus, and fire short bursts to beat surge; get low and shoot up for separation, keep fins up to avoid silt, and never touch or stress marine life; for super-macro, pre-focus with a wet diopter, brace gently, and consider tiny stacks only in dead-calm water; rinse gear thoroughly, keep O-rings immaculate, and run a quick leak test before every entry. Whether you’re framing a pygmy seahorse’s eye ring, the rhinophores of a nudibranch, or the micro-patterns on a crab’s claw, the best macro lenses for underwater photography pair dependable AF, comfortable working distance, and port/diopter compatibility—so your small ocean subjects look tack-sharp, clean, and gorgeously lit beneath the surface.