The Olympus Tough TG-620 is a waterproof compact announced in February 2012 alongside the flagship TG-820, both introducing Olympus's iHS processing to the Tough line. It went on sale that spring as the mid-range rugged option, in a choice of bright colours.
It is waterproof to 5 metres, shockproof against 1.5-metre drops, freezeproof to -10C and dustproof, built around a 12MP back-illuminated CMOS sensor, TruePic VI processor, a 5x 28-140mm equivalent internal zoom (nothing protrudes), a 3-inch screen and 1080p video. The BSI sensor gave it noticeably better low-light and underwater results than the CCD Tough models it replaced.
Rugged compacts like the TG-620 have proved oddly durable on the used market - they are the sensible cheap holiday and snorkelling camera nobody's phone can follow into the pool, and Olympus's Tough series is the benchmark name. The TG-620 hits a sweet spot of CMOS-era image quality at pocket-money prices, hence its steady presence in UK listings.
With any used waterproof camera, the seals are the purchase: open both the battery/card and connector doors and inspect the O-ring gaskets for nicks, flattening or dried-out rubber, and look for tell-tale white corrosion on the battery contacts that betrays a past flood. Check the lens window for scratches (it lives unprotected on the body face) and internal fogging, verify the buttons all click home - grit ingress stiffens them - and treat waterproof claims on a decade-old camera as aspirational until you have replaced or greased the seals; test it in a sink before trusting it in the sea.