Hidden among the sharp lava cliffs on the Big Island of Hawaii’s Kona coastline are lava depressions that fill with seawater each day at high tide. As the tide recedes, the isolated pockets of water become tidepools, miniature worlds containing a bounty of life. These overlooked basins at the ocean’s edge are often only a few feet in diameter with only a few inches of depth. Living in this rugged environment with low oxygen, hours exposed to the sun, and increasing water temperature is certainly not easy for marine life but makes for excellent observation and photography. Here’s a peek at what to expect from Hawaii tidepool marine life.

Viewing lava tidepool life

By carefully leaning into the shallow water at low tide, photographers and lovers of the undersea world can get a glimpse into the delicate and unique ecosystem of Hawaiian tidepools. Though the sharp lava and slippery, algae-covered rock trails can create a challenging approach in some areas, you can view and photograph lava tidepools year-round at low tide by either sitting at the edge of the pool or sliding into the pool with a mask and snorkel, depending on preference and depth. Here’s some of the life you might see.

Variable sargassum (Sargassum Polyphyllum)

Though the inhabitants of tidepools vary greatly, a common find is some type of brown or green algae. Seeing this variable sargassum from a distance, extending to the surface of the water, is exciting because marine life thrives under and within the wrinkled golden blades and spherical berry-like gas bladders, standing erect in the tidepool like a forest. Fish use this endemic Hawaiian brown algae like coral, for places to hide and to easily camouflage themselves from predators.

Marbled shrimp (Saron Marmoratus)

Snorkelers and night divers most frequently see marbled shrimp, but they are exciting finds anytime, with extravagant bands of color and an overall color change from day to night. At night, they seem to take on a reddish hue, but these two are showing the whiter daytime coloration. Males and females have distinctly different characteristics. Males have claw-bearing limbs that are extraordinarily long — longer than their own body length. Females instead have tufts of bristles on their first pair of legs and bodies. These two females were sparring, tucked back in a crevice between two rocks.

Zebra blenny (Istiblennius Zebra)

Zebra blennies are one of the more common and obvious endemic dwellers in Hawaiian tidepools. The fish has a variable color pattern, from solid dark gray or blue, to barred or mottled patterns. They routinely zip around the pool freely, stopping to stare at the curious snorkeler, then bounce into a head down orientation, with their massive mouths agape, and feast on detritus covering the sides of the lava rocks. These fish are not confined to one tidepool for life but can wriggle out of the water and leap up to two feet in the air to another tidepool.

Flat rock crab (Percnon Planissimum)

Hidden on the underside of smooth, rounded basalt boulders, you can see brightly colored flat rock crabs during day or night in shallow water. They move quickly and can wedge their flat body into exceedingly small crevices when feeling threatened. A pair of yellow and red walking legs extending from between two rocks may be the only thing a snorkeler sees at first, but with patience, the whole crab may reveal itself.

Stocky hawkfish (Cirrhitus Pinnulatus)

Using the gaps between boulders for protection, the stocky hawkfish occasionally inhabits deeper tide pools, feeding on small invertebrates, snails, and fish. Color patterns can vary, but there are often rich hues of red and aqua present. The stocky hawkfish does not seem to appreciate the company of snorkelers, so approach slowly if you want a close -up view.

Glass anemone (Aiptasia Pulchella)

Glass anemones are abundant on walls and in holes with long, translucent brown, yellow or pink tentacles that seem to dance as they extend toward the surface of the tidepool. Understandably, the species name means “beautiful.” These fascinating anemones, made up of hidden communities in dark crevices, can procreate rapidly by detaching bits of tissue from their foot to multiply into baby anemones or give live birth through the mouth.

Left-handed hermit crab (Calcinus Laevimanus)

Found foraging in no more than a few inches of water, this tiny crab is one of the more common tidepool hermit crabs in Hawaii. When feeling threatened, the crab fully retreats its soft abdomen and body within the chosen shell, often a snail shell, then locks the door to its house by raising its enormous left claw to seal the shell’s opening. At only ¼-inch long, look closely to find these colorful crabs.

By guest author Christine Regent West

Christine is a naturalist, photographer and videographer, USCG 100-ton Captain and Cressi Ambassador. She seeks to explore and document stories about the extraordinary, places poorly understood, often beneath murky, cold water in places like Alaskan lakes, rivers and fjords. Christine currently dives on expedition ships around the globe for Lindblad-National Geographic Expeditions. Check out more of her work at her website and on Instagram.

UC San Diego Team Publishes Guidelines For Post-Coronavirus Diver Medicals

Divers who had Covid-19 symptoms may need thorough medical assessments before returning to diving (Photo: Shutterstock)

By Mark ‘Crowley’ Russell

A new study by researchers at the University of California, San Diego has given updated guidelines for the conduct of scuba diving medicals for divers who may have suffered from Covid-19.

The report, ‘Diving after SARS-CoV-2 (COVID-19) infection: Fitness to dive assessment and medical guidance‘, was published in the journal Diving and Hyperbaric Medicine after a team led by lead author Dr Charlotte Sadler, of the Department of Emergency Medicine, Division of Hyperbaric Medicine at UC San Diego’s School of Medicine, analysed the known effects of Covid-19 on the human body, together with comparative research based on the long-term effects of similar viruses.

Problems for divers who have been infected with SARS-CoV-2 were postulated shortly after the pandemic became widespread. A medical doctor in Austria published a letter in German magazine Wetnotes as far back as April 2020 with concerns that the long-term physiological effects of Covid-19 on patients – who might otherwise be completely asymptomatic and feeling entirely normal – may go unnoticed without a more extensive medical investigation than would usually be required for divers.

‘The diving medicine community is presented with the challenge of performing fitness to dive evaluations in the context of a disease in which the natural history is currently unknown,’ writes Dr Sadler in the report. ‘In what is known of [Covid-19’s] pathophysiology the pulmonary, cardiac, and [blood-clotting] effects seem to be very relevant to divers.’

While Covid-19 primarily affects the respiratory system, which is already a concern for divers, it has been shown that severe cases of the disease can cause damage to the heart, ‘potentially increasing the risk of barotrauma, and also decreased exercise tolerance and increased susceptibility to cardiac events such as heart failure, pulmonary oedema, and arrhythmias,’ according to the report.

The recommendations for medical examination are split into four categories, depending on the severity of illness experienced by each diver. Category 0 is defined as a diver who had never experienced any symptoms of the disease, even if they had tested positive for Covid-19; Category 1 is for divers who had a ‘mild’ case, where hospitalisation and the provision of emergency oxygen were not required; Category 2 for a ‘moderate’ case, in which treatment for Covid-19 included the provision of emergency oxygen but not mechanically assisted ventilation; and Category 3 for the most severe cases, for those who required treatment in an intensive care unit.

Regardless of the category in which a diver might belong, they must be entirely asymptomatic and have ‘returned to their baseline exercise tolerance’ before undergoing a medical evaluation. In other words, they should be able to perform the same level of exercise as they were prior to infection with SARS-CoV-2 without getting easily winded or requiring longer recovery times. ‘Further testing and investigation’ should be carried out if divers exhibit ‘even minor deviations from their baseline.’ Since that baseline will differ between individuals, physicians who are concerned about a diver’s ‘self-reported exercise level’ should check to see if it ‘warrants an appropriate exertional test for diving.’

The level of medical examination required for each category is described fully in the UC San Diego Guidelines for Evaluation of Divers document but ranges from ‘no additional testing required’ and following the general RSTC (or equivalent) guidelines for Category 0 divers, to echocardiograms and measurement of oxygen saturation levels while exercising, and blood tests to check for the presence of damage to the heart for those in Category 3.

Divers who exhibit any symptoms of either Covid-19, or potentially what is now being referred to as ‘long Covid’ – ie continuing symptoms of conditions caused by the initial infection – are to be automatically precluded from diving. According to the report, however, this does not necessarily represent a lifetime ban on diving ‘as many of the sequelae [(ongoing conditions)] which are currently disqualifying (such as abnormal CT scans) may resolve over the next 3-6 months and re-testing may be indicated.’

The advice from the team at UC San Diego follows on from that given by the Belgian Society for Diving and Hyperbaric Medicine in April, recommending that divers wait up to three months before returning to the water following any coronavirus-related symptoms. As the UC San Diego report notes: ‘It is likely that all divers who have contracted Covid-19 will require a medical evaluation prior to a return to diving, with emphasis upon pulmonary and cardiac function as well as exercise capacity.’

The guidelines issued by the hyperbaric physicians of the University of San Diego can be downloaded in full from the UCSD website. The original paper, ‘Diving after SARS-CoV-2 (COVID-19) infection: Fitness to dive assessment and medical guidance’ by Dr Charlotte Sadler et al can be read in the Diving and Hyperbaric Medicine online journal.