246 
carried to the surface by a diver. The substrate 
was examined for special features such as tex- 
ture and chemical composition (e.g., CaCOs or 
basalt). It was possible to draw bottom profiles 
of the substrate in situ, using a grease pencil 
and plastic slate. 
CURRENTS: Currents were measured in three 
ways. Data off Sandy Beach, Oahu, and Kaena 
Point, Oahu, were collected with the aid of the 
research vessel "Neptune I.” In these cases, sur- 
face currents were measured by tracking the 
movement of drifting current crosses. 
The Carruthers’ Current Cone (Carruthers, 
1957) was used when sampling was carried out 
in an 18-foot skiff. It operates on a wa er- 
resistance principle, much like a flag fluttering 
in the wind. Attached to a stationary line, the 
cone is lifted by the current at an angle propor- 
tional to the intensity of flow. At this point a 
dissolving cube of sugar triggers the device so 
that a reading is obtained. Observations of this 
instrument during use showed that the angle of 
the cone at any one instant was highly variable, 
subject to the oscillatory movements of surge 
PACIFIC SCIENCE, Vol. XIX, April 1965 
and swell. Hence, under very rough conditions 
this instrument is not accurate. 
The third, and simplest, method of measuring 
current (and the most accurate) was timing the 
horizontal drift of suspended particles over a 
known distance. Currents less than 0.5 knots 
were referred to as slight, from 0.5 to 1.5 as 
moderate, and over 1.5 knots as heavy. 
SURGE: Surge is herein defined as a back-and- 
forth movement of water over short distances 
which is generally caused by long waves (swell). 
It is dependent upon the amplitude and the 
wavelength of the swell. The period of oscilla- 
tion usually varies between 6 and 16 seconds. 
The movement of water particles in waves with 
short wavelengths is nearly circular at the sur- 
face. The radii of these circles decrease expo- 
nentially with depth and are imperceptible at 
a depth which equals the wavelength (Sverdrup, 
Johnson, and Fleming, 1940). In waves with 
longer wavelengths, the movement of water par- 
ticles follows a more elliptical orbit. 
When waves begin to "feel” the bottom, the 
movement of water particles close to the sub- 
