How Is Decompression Handled on a 300-Foot Dive? Who Does Those Dives and How They're Run

The short answer

There is no one number. Decompression time from about 300 feet (roughly 90 meters) depends far more on how long the diver stayed there and what gas they breathed than on the depth alone — a brief visit and a day's work at the same depth produce completely different obligations. It also depends on the method: a short deep dive is decompressed over a period of hours in the water or in a chamber, while saturation diving inverts the problem entirely and decompresses the team once, over a period measured in days, at the end of a work assignment.

This page explains how deep-dive decompression is organized and who does it. It is not a planning resource, contains no schedules, and is not a guide to attempting anything at depth.

300 feet is outside recreational diving by a wide margin

Recreational training standards, coordinated internationally through the WRSTC minimum course content standards, are built around no-decompression diving within a shallow depth band — the familiar recreational ceiling is 130 feet, and most certifications authorize considerably less than that. The published no-decompression air tables from the NOAA Diving Program stop well short of 300 feet, because air is not an appropriate breathing gas anywhere near that depth in the first place.

At those pressures, work is done on helium-based mixtures with carefully managed oxygen fractions, usually supplied from the surface rather than carried on the diver's back, by commercial, military, or specialized technical teams. The difference between that world and a recreational certification card is explained in recreational certification vs. commercial diving credentials.

The two ways deep decompression is organized

Bounce diving. The diver descends, works for a limited period, and ascends through a staged decompression profile — in the water, in a bell, or in a deck chamber after a surface transfer. Because the diver's tissues never come close to equilibrium with the depth, the obligation stays finite and is driven mostly by bottom time. Add time at depth and the decompression grows disproportionately, which is exactly why a short bounce and a long work dive are not the same question.

Saturation diving. Past a certain exposure, tissues approach equilibrium with the ambient pressure and stop taking on meaningful additional gas. Once a diver is saturated, decompression time no longer grows with more days at depth. The economic logic follows: crews live under pressure in a surface habitat, commute to the worksite in a bell, and decompress once at the end of the assignment — a slow, continuous process measured in days rather than hours.

What the regulations require

In the United States, working dives of this kind fall under OSHA's commercial diving rules in 29 CFR Part 1910 Subpart T. Subpart T defines mixed-gas and saturation diving, sets requirements that scale with depth and with whether the dive exceeds no-decompression limits — including decompression chamber provisions — and imposes obligations on staffing, equipment, procedures, and record-keeping. The regulation is the operative document; there is no informal version of it.

Federal scientific diving works within its own framework. The NOAA Diving Standards and Safety Manual sets depth authorizations, decompression procedures, and medical requirements for NOAA divers, and consensus standards such as the AAUS Standards for Scientific Diving do the same across member scientific programs. In all of these, a diver does not simply choose a depth — authorization is granted incrementally, backed by documented training, medical evaluation, and a written dive plan.

Why the question is usually really about something else

People who search for this are often trying to calibrate a sense of scale: how far beyond ordinary diving deep work actually sits. A useful way to put it is that decompression at recreational depths is a table lookup and a safety stop, while decompression from 300 feet is a staffed operation with chambers, gas logistics, communications, and a medical support plan attached. The clinical background on decompression illness — the reason all of that apparatus exists — is summarized in the CDC Yellow Book chapter on dive-related injuries.

For the shallow end of the same concept, how to read a no-decompression dive table covers how recreational planning stays inside limits rather than incurring an obligation at all.