14.0 GENERAL

The development and use of underwater support platforms has evolved from recently acquired knowledge of basic diving physiology (Section 2), saturation diving (Section 12), and breathing media (Section 5). The reader is directed to these sections for appropriate detailed discussions. The principal purpose in using underwater platforms is to extend the diver's usefulness while submerged. One way is to provide a means to increase the diver's time on the bottom, either by permitting him to live in a submerged habitat or by reducing the time required for descending and ascending. Another way is to increase the diver's mobility and lessen his physical activity, thereby expanding his productive time under water.

This section discusses two types of underwater support platforms and two types of underwater propulsion systems.

mitting unlimited access to the environment. Living and working under water, the scientist. is capable of making observations over long periods of time and of designing sophisticated experiments which cannot be performed in the laboratory. It should be realized, however, that the advantages of using a habitat depend upon the nature and objectives of the particular diving operation. It is therefore necessary to evaluate a particular habitat design in relation to the specific diving project in which the habitat is to be used (High et al. 1973).

A recent report (University of New Hampshire 1972) describes those features of an underwater habitat which are considered desirable based on a nationwide survey. Recognizing that such characteristics must be tailored to mission objectives those desirable features of a general nature are summarized in Table 14-1. While detailed specifications are not appropriate in this manual the general guidelines provided in Table 14-1 will acquaint the reader with certain features to be expected in habitats of the future.

In designing and selecting habitats for use in marine science programs, both technical and logistical criteria must be applied if systems are to match missions. The report cites six major criteria in evaluating a habitat system. These are mission adequacy, operational adequacy, flexibility, technical confidence, safety, and cost. These criteria are summarized in Table 14-2 (University of New Hampshire 1972). Further details of habitats, their design, and their use may be found in Table 14-3 (Parrish 1972).

No attempt will be made to provide detailed outlines of specific scientific projects accomplished to date using underwater habitats. For these details the reader may consult Pauli and Cole (1970) and Miller et al. (1971).

Projects best undertaken from underwater habitats are those requiring long term in situ monitoring of environmental paranieters or organisms. Although

in shallow water these activities may be undertaken from the surface, it often becomes more economical and feasible for the scientist to work or observe from an underwater chamber. As scientists learn more about the advantages and techniques of habitat-based operations, they should be able to increase their in-water time and efficiency two- to three-fold. Beginning at about 80 feet the burdens of decompression in conventional diving become prohibitive. Ecological community assessments for example may require many hours on the bottom. For this type of activity, saturation diving becomes an efficient tool.

There is also a need in the marine sciences for nonsaturation underwater work chambers and simple bottom platforms. Such facilities, although restricted in size and capability, are excellent for some shallow water projects as well as serving as a facility for preparing scientists for saturation diving. The scientist-diver can simulate saturation and thus acquire the necessary "self-discipline" and training required for total saturation. Also, various research techniques and experiments can be field tested without the complexity, expense, and total commitments of a saturation dive.

SUBLIMNOS (Figure 14-1), a Canadian habitat, is an inexpensive shallow-water habitat built for the purpose of creating greater accessibility for a longer duration to the budget-limited scientist. The habitat provides a "day-long" work capability for up to four divers. The upper chamber is nine feet tall and eight feet in diameter. Access is afforded through a 35 inch hatch in the floor of the living chamber.

SUBIGLOO (Figure 14-2) also Canadian, has been used in Arctic exploration programs with great success in 1972 and 1974. It is constructed of two 8-foot acrylic hemispheres on aluminum legs. It affords an unrestricted view thus serving as an excellent observational platform (Stang 1974). LAKE LAB (Figure 14-3) was designed for 48 hours of continuous operation for two persons to depths of 30 feet.

LAKE LAB operations are controlled from a shore-based mobile van. The van is equipped with low and high pressure air compressors, high pressure air storage units, a habitat control console, communicators, first aid and emergency supplies. diving equipment lockers, work bench, and other equipment necessary for support of the habitat operation.