Most of the Hong Kong people might have heard a country, Costa Rica, by watching the World cup, but I knew it from seeing a documentary that shown on Hong Kong Space Museum. It says that there is a large group of scalloped hammerhead sharks that swim shallowly around a remote island, Isla del Coco (Cocos Island).
Cocos Island 位於哥斯達黎加西岸，即位處中太平洋，距離哥斯達黎加海岸550公里(km)，一般船程要32至36小時。島上絕大部分地方由熱帶雨林覆蓋，而此島及其週邊海域自從1978年已成立為國家公園，島上現在只有少數林護員(park rangers)駐守，島上不設酒店，所以訪客都只可住在船上。島上最高的山峰有575米（M）。除了不准捕魚，還嚴格限制訪客數量，如現在只許2間公司經營4艘宿船到此島潛水旅遊，而且限制同一時間最多只有3艘宿船在此島範圍潛水及活動。而私人遊艇經事前申請也是可以到此停留。
|Cocos Island aerial view|
Cocos Island is at the western side of Costa Rica, where is near the equator of the Pacific Ocean. The distance of this island from the coast of Costa Rica is 550km. Visitors usually take about 32 to 36 hours travelling time by common vessels. It is covering by tropical rainforest mostly. As this island and its surrounding ocean have been declared as a national park since 1978, it only has park rangers on duty. There has no hotel, such that all visitors can only live on board. The government also implements a lot of regulations to protect this area, such as fishing is prohibited and she only licenses two companies with 4 commercial vessels that can operate tourist visiting regularly. The regulations also limit at most three vessels that may stay at this island area at the same time.
Under such protection, this island keeps its wild environment except the remains of pirates who had occupied and lived for three centuries, before the government has governed this island. Since the pirates had left, there had a rumour, which said that a treasure was hidden in somewhere. Nowadays, treasure hunting on island is prohibited of course. That the pirates bought introduced species to the island has been the most negative impact to the island, because birds have been hunted by them that did not have before.
過往我在外國潛水時和很多外國人傾談，說到理想的潛水性地，Cocos Island 是最常提及的名字。而距離680公里外的以達以文進化論聞名的加拉帕戈斯群島也是很有名。因受不同的水流的影響，加拉帕戈斯群島的水溫通常較Cocos Island 低很多，平均是22度攝氏，而Cocos Island 是25度。
In the past, when I talked with the foreign divers during overseas diving, they usually name Cocos Island as a dream place for diving. The second is Galapagos Islands where is just 680 km from Cocos Island. Because of having influence by difference currents, their water temperature has a large difference despite such close distance. In average, water temperature of Galapagos Islands is 22 degree Celsius while Cocos Island is 25 degree.
錘頭鯊為何在此處淺水出現？其實錘頭鯊或雙髫鯊的分佈很廣，無論太平洋及大西洋，甚至紅海也看到他們出沒，但一般也只在深水或不常見。錘頭鯊可分為幾個品種，分別是 扇形雙髻鯊, 流線雙髻鯊, 細眼雙髻鯊, 巨雙髻鯊 及 窄頭雙髻鯊。我們今次看到的都是扇形雙髻鯊這一個品種。
|Scalloped hammerhead shark|
Why do hammerhead sharks come here and swim shallowly?As hammerhead sharks are a widely spread species, they may be found in the Pacific ocean and the Atlantic Ocean, I even saw once in the Red sea, but they swam very deep. Hammerhead shark has five species, which are Scalloped hammerhead shark, smooth hammerhead shark, small eye hammerhead shark, Great hammerhead shark, and bonnethead shark. They were scalloped hammerhead shark that we saw during this trip.
Cocos Island吸引牠們來，是因這裡是一天然「診所」（cleaning station)，如鯊魚或其他大型魚類生了寄生蟲或有損傷，珊瑚區很多時會有醫生魚(如黑鼻蝶魚,天使魚或各種濑鱼等)幫助鯊魚等魚類咬走寄生蟲及傷口死皮。這時錘頭鯊會游近水底礁，減慢速度及身體作出擺動，以通知醫生魚來。因鯊魚是軟骨魚是沒魚鰾，如牠們要保持某一水平便需不斷游泳，所以當鯊魚在交配中，會除除下沉直至到水底或完事。部分鯊魚甚至要不斷游泳以使水能流經鰓以呼吸。
Hammerhead sharks like other fishes may get sick or parasitic infection, so they need to go to underwater clinic periodically, which is cleaning station, where gathers many cleaner fishes, such as barberfish, angelfish, or wrasses, etc. They eat the dead skin of wound or parasites. When sharks come close to reef, they swim slow down and signal to the cleaner fishes. Because hammerhead shark is soft-bone fish that has no swim bladder, it needs to keep swimming all the time to maintain its level. Therefore, when hammerhead sharks are mating, both of them descend slowly to bottom, because they cannot swim and mate at the same time. Some shark's species even need to keep swimming for sucking sufficient water through their gills.
本來Cocos Island是一個全年都識合潛水的潛點，不過昨年(2018)是有點失色，因昨年正處於厄爾尼諾(El Niño)週期，這代表東太平洋水溫比平常高。我到達時發現水溫達攝氏27度，這不是牠們喜歡的水溫。所以數量比想像中是少了很多，特別是游近礁的數量非常有限。在這裡拍攝牠們的泳姿是最理想的，因說過牠們會游得較慢及接近鏡頭。根據不同的潛點，我們會停留在20至30米的深度，以守株待兔的方式等牠們游來。
Since Cocos Island is at tropical zone, there can be diving year-round, but it was not the best season last year (2018) when I have dove, because there was during the cycle of El Niño that means the water temperature of east Pacific ocean is higher than normal. When we have arrived, we found that the water temperature is 27 degree Celsius that is too high for hammerhead sharks, such that the number of sharks was much less than my expectation. There were not too many sharks that swam closed to the reef where is the best place to take photo and video, as they swim slower. According to difference dive sites' formation, we stayed between 20 to 30 meters depth to wait for their coming. Despite wrong timing, Cocos Island keeps its guarantee, as I could have taken some shots that they swam to me close enough. We also saw one poor hammerhead shark which has been being entangled by a fishing net and some lines have deeply cut into its dorsal and tail fins.
|Rosy lip batfish|
Star of CocosBeside large fishes, there is a small fish that has sharp rosy lip, which like a woman who has lipstick's makeup, and walking by fins. This species can be spotted in Cocos Island and Galapagos Islands. They live on shallow sandy bottom and feed on small fish. Despite they usually walk, they can swim by swinging their tail. They are also good in posting.
深潛的體驗娛樂潛水的最深深度是40米，任何正式訓練都提醒不能超越。如要挑戰，那便進入技術潛水，無論裝備及訓練都不同。在Cocos Island 營運的其中一間公司，特別訂做了一架主要作為娛樂用途的潛艇給未有機會挑戰深潛的人可親身體會水深三百米的環境。這公司的主要股東本身是一知名水底攝影師，船上特別預留私人房間，他幾乎是每個行程都會參加。他建做這潛水艇也有科研的考慮所以艇外亦有一機械手臂。而他亦因有這潛艇，得以發現一軟珊瑚家族(family)，並在2012在科學上證實，這新家族的第一個品種便以他的名字命名。
Deep dive experienceThe maximum depth of recreation diving is up to 40 meters. Diving instructors always tell not to excess this limit. If anyone wanted to challenge this limit, it would be technical diving that is required special training and equipments. One company that runs in Cocos Island built a submarine, which provides deep dive experience to anyone who doesn't have deep dive training. This submarine can be used by both recreational and researching purpose, so it is equipped with a robot arm and a high definition camera. Using this submarine, the founder who built this submarine found a new family of soft coral. After this exploration has been confirmed scientifically in year 2012, his name names to the first species of this family.
The most important part of this submarine is its spherical dome, which makes by 4 inches acrylic. When this dome was modeled, they controlled the density of acrylic is as same as sea water, such that the people do not realize its exist underwater. It may serve two guests with a pilot for each descending. When it is a researching trip, one of them must be a robot arm technician.
During diving, our mask enlarges the objects that we see, but the dome shrinks the object to two third of its original size.
Safety is the most concern to the operators. They have been lucky that this submarine has never happened accident. Each guest must be weighed for adjusting the balance of submarine and given a briefing when an emergency occurs. This briefing tackles 2 situations:
1. Electric fire
2. If pilot were unconscious, how the passengers would take control to the submarine and surfacing.
Of course, we have never used this.
Every trip, it requires two pilots to operate the submarine, one on surface and the other inside the submarine. Both pilots need to communicate frequently to report the monitoring data such as temperature, level of carbon dioxide and depth. The communication is through wireless that may transmit over several hundred meters. There is another assistant who works for attaching and detaching cables and taking photos to the guests from outside of the submarine.
The design depth of this submarine is 400 meters, but it only goes to 300 meters for recreational use. In this depth, it has been beyond the twilight zone that has no light. The difference between SCUBA diving and submarine is decompression. As the ambient pressure keeps in one atmosphere pressure, the absorption of nitrogen has no difference with on land, such that no decompression is required and the ascending rate is faster.
This submarine uses two large bladders to control the ascend and descend and air is circulated internally, such that no air is emitted from the submarine, but it can be done if the pilot wants.
|Yellow conger eel|
|Inside the submarine on surface|
|Inside the submarine under 300m|
At this depth, colour of creatures has diminished except those are living both shallow and deep. I hoped to see a large group of hammerhead sharks passing by us, ragged-tooth shark and prickly shark that only live in deep sea before the descend, but non of them has been seen. Fortunately, we saw some creatures that live in deep such as jellonose fish, frogfish and king crabs.
We took flights to the capital of Costa Rica, San Jose, via Los Angeles and stayed one night. The operator hires an agent to pick up the guests on the day of departure between 8am and 1pm to the seaport, Puntarenas, where is the base of the vessels. Guests stay on the vessel for ten days usually and the operator offers Scuba diving, submarine experience and land trip to the island.
VISA: BNO holder needs visa, but it can be exempted with valid US' visa. HKSAR's passport doesn't require visa, but you also require an US' visa, if you transit through US' airports.