These devices are not used for recreational diving. They are primarily used for shallow commercial work such as cleaning boats, working on docks, etc. I guess you could use one to bounce around a shallow reef, but then again, there are a lot of things that are possible, but not practical. As with any underwater activity, there should be several layers of safety in place, such a person on the surface to monitor the compressor, etc.
When commercial divers use surface-supplied air beyond 100ft, they are accompanied with a team of people to assist in the dive.
Here's a neat read from ww.osha.gov/pls/oshaweb/owadisp.show_document?p_table=DIRECTIVES&p_id=3449
# 29 CFR 1910.425 Surface-supplied air diving.
1. 29 CFR 1910.425(b) Limits.
1. 29 CFR 1910.425(b)(1). The maximum depth for surface-supplied air diving is 190 fsw, except that surface-supplied air dives with bottom times of less than 30 minutes may be conducted to a maximum depth of 220 fsw.
2. 29 CFR 1910.425(b)(2). A decompression chamber is required (available within 5 minutes from the dive location) for dives deeper than 100 fsw, or any dive that requires planned decompression.
NOTE: Decompression chambers and diving bells, when used as a recompression facility, shall meet the criteria specified by 29 CFR 1910.423(c) and 29 CFR 1910.430(f).
3. 29 CFR 1910.425(b)(3). A diving bell is required for dives with an inwater decompression time greater than 120 minutes, except when heavy gear is worn or diving is conducted in physically confining spaces.
2. 29 CFR 1910.425(c) Procedures.
1. 29 CFR 1910.425(c)(1). Each diver is required to be continuously tended while in the water.
NOTE: 29 CFR 1910.425(c)(1)(i) requires that a separate dive-team member tend each diver in the water when the dive exceeds 100 fsw or is outside the no-decompression limits. The increased hazards and complexity associated with deeper or longer dives may compromise diver safety if a tender is responsible for tending more than one diver.
2. 29 CFR 1910.425(c)(2). When diving is conducted in enclosed or physically confining spaces, another diver shall be stationed at the underwater point of entry.
3. 29 CFR 1910.425(c)(3). This paragraph requires that each diving operation have a primary breathing-gas supply that is sufficient to support divers for the duration of the planned dive, including decompression.
4. 29 CFR 1910.425(c)(4)(i), (c)(4)(ii), and (c)(4)(iii). For dives deeper than 100 fsw or outside the no-decompression limits, each diver must: be tended by a separate dive-team member; have a standby diver available at the dive location while the diver is in the water; and have a diver-carried reserve breathing-gas supply, except when heavy gear is worn.
5. 29 CFR 1910.425(c)(4)(iv). A reserve breathing-gas supply is required at the dive location for dives deeper than 100 fsw or outside the no-decompression limits.
NOTE: The reserve breathing-gas supply required at the dive location must be on line and ready for use, and its source must be independent of the primary breathing-gas supply. The reserve breathing-gas supply must be of sufficient quantity and pressure to allow each diver to complete any planned decompression schedule.
6. 29 CFR 1910.425(c)(5)(i) and (c)(5)(ii). For surface-supplied air diving with heavy gear, deeper than 100 fsw, or outside the no-decompression limits, an extra breathing-gas hose must be available to the standby diver, and the hose must be capable of supplying breathing gas to the diver in an emergency. Also, an inwater stage must be provided for the diver(s) in the water.
7. 29 CFR 1910.425(c)(6). A diver-carried reserve breathing-gas supply must be provided to a diver in the water when the diver is prevented by the configuration of the dive area from ascending directly to the surface (i.e., when the diver does not have "free access to the surface"), except when the diver wears heavy gear or when the physical space does not permit the use of such a breathing-gas supply. The diver-carried reserve must be sufficient under operating conditions to allow the diver to reach the surface, or another source of breathing gas, or to be reached by a standby diver. Heavy-gear diving is exempted from these provisions because the gear carries its own reserve.
NOTE: For vessels without longitudinal (horizontal) stabilizers, "free access to the surface" means that the diver is diving above the turn of the bilge; for vessels with longitudinal stabilizers (usually found on military combat vessels), "free access to the surface" means that the diver is diving above the stabilizers.
3. Commercial surface-supplied air diving with one diver in the water requires a minimum of three dive-team members: a DPIC (see 29 CFR 1910.410(c)), and a diver "who shall be continuously tended [by a tender other than the DPIC] while in the water" (see 29 CFR 1910.425(c)(1)). For surface-supplied air diving that is 100 feet or less and does not involve planned decompression, a standby diver is not a specified requirement for every dive. However, based on the requirements of 29 CFR 1910.421(d) Planning and assessment, the hazard analysis and assessment of the dive will dictate the use of a standby diver when underwater conditions and hazards or potential hazards involve: proximity to an underwater suction, no free access to the surface, the possibility of diver entanglement or entrapment, or unknown bottom conditions. If a standby diver is required (such as when these conditions are present or for depths that exceed 100 fsw), these duties may be performed by the DPIC or the tender. A tender who is a qualified diver can be the standby diver; for a three person dive-team, the DPIC would assume tending duties when the standby diver (tender) is in the water. A DPIC who is a qualified diver also can be the standby diver, provided that another dive-team member is at the dive location. This dive-team member must be trained and capable of performing the necessary functions of the DPIC, when the DPIC is in the water as the standby diver.
NOTE: In establishing the number of dive-team members required for a dive, proper consideration must be given to 29 CFR 1910.421(d) Planning and assessment, 29 CFR 1910.421(e) Hazardous activities, and 29 CFR 1910.422(b)(3). This latter provision requires employers to provide a means to assist an injured diver from the water (such as an inwater stage, small boat, or stokes basket) or into a diving bell, that may necessitate additional dive-team members.
