Deep diving and when you need more training

Every recreational scuba certification has a depth limit, and the first one you're likely to hit is the 18-metre line that comes with Open Water. Beyond it, the way you plan and manage a dive changes — and so does the risk.

Going deeper isn't just "more of the same". The water pressure rises, the gas you breathe changes what it does to your body, and the decompression obligation grows. This is why agencies push you into an Advanced course before the signs allow the jump to 30 metres.

The list below pulls the deeper, more challenging sites from our database, ranked by overall score. Check the certification requirement on each site page before you commit.

The depth ladder

A typical Open Water course qualifies you to 18 metres. The Advanced Open Water course adds an elective that brings qualifying divers to 30 metres. Beyond that, you're into sub-30-metre territory usually served by a deep-diving specialty and often technical — or "tech" — diving with decompression.

Nitrogen narcosis and gas

At depth, the nitrogen in air becomes narcotic — the deeper you go, the more it affects thinking and judgement. Deep divers often switch the gas (for example, heliox or trimix) or accept the narcotic effect and plan accordingly. This is a big part of why coping with depth is a skill you're trained into, not born with.

Decompression obligation

A deep dive uses up no-stop time quickly; stay down too long and you owe decompression stops on the way up. Recreational divers use a dive computer to track this and keep within the no-decompression window. Ignore it and you risk a hit — the single most avoidable serious injury in diving.