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Costa Rican Apparent UAP Accidentally Photographed During 1971 Aerial Survey-A new explanation which makes more sense than existing suggestions

Jack Sliwa    Technologist     05/18/21



Thanks to Wikipedia Commons For Above Photo


    During September 1971, in the early morning when the sun was low on the horizon, an aerial survey plane 10,000 feet over Lago de Cote Lake in Costa Rica photographed what appears to be a 683 foot diameter UAP either on the lake water or just above the water. Several investigators have looked into this case. Perhaps the best investigation was done by Richard Haines and Jacques Vallee and reported in the Journal of Scientific Exploration Vol 3 No 2 pp 113-131 whose link is below. It was a good effort however there are still

major open points which make little sense.


    The biggest question in my view is that nobody saw a 683 foot UAP in the sunlit morning on or just above the lake yet after the first event and during a second event residents easily spotted far far smaller apparent “periscopes” sticking out of the water surface having a relatively tiny size of approximately 1 meter or 3 feet. I don’t think the first event was ever visible to local residents on the shore (or on the lake). It was however 

clearly visible to the aerial survey camera which was of high quality and was operating well. The above photo shows that. Secondly, such a huge craft would likely have caused waves upon the shore and significant water  displacement which also wasn’t noticed. The lack of a UAP shadow makes it clear the UAP was near or on the water. The lake surface was nearly smooth at that time.


    This natural crater lake is not very deep (6-18 meters or roughly 18-54 feet) compared to the “apparent” 638 foot diameter of the UAP. Presuming the apparent 638 ft UAP had a typical UAP disc shape it would have been somewhere between at-least 64-100 feet in height. Thus it almost certainly would not be able to submerge completely even if it wanted to. The lack of witnesses and the submergence problem don’t support a 638 ft UAP on or under the water. If the UAP were 638 ft in diameter and 64 feet (at least) in height it would be at-least 10 feet too tall to totally submerge. Thus if one edge of the purported 638 ft UAP is indeed partially submerged it would be resting on the bottom.


    The entire phenomenon can be explained in the following alternative manner. The UAP was totally underwater AND it was far smaller than 638 ft in diameter. I estimate from the photo that the submerged UAP was between 40-60  feet in actual diameter-a common size regime. So what is causing the 638 ft diameter reflections? It’s the water surface being excited by the submerged UAP. There are numerous cases of submerged (or hovering) UAPs causing the water’s surface to be excited with fine or small features which would be highly reflective with this low angle lighting. On an otherwise placid lake surface this would dramatically increase the reflectivity of the water’s surface as seen by the aerial survey plane especially given the low sun angle. Thus the UAP is likely propelling itself or is using its levitation or underwater motive power to maintain a controlled depth. It will be noted that the bright areas could be regarded as UAP power being sent backward in a symmetrical manner as for a ships wake. No matter how the power is output there will be a signature on the lake surface due to acoustic underwater reflections and shallowness. I note that a UAP of 40-60 feet diameter would have a height of about 4 to 9 feet and be very easily fully submerged and moving laterally underwater but not on the bottom-even in the shallow lake portions.


    This explains why no lakeside residents saw it and why the surface lake disruptions seen from overhead were so large in lateral extent compared to the real much-smaller UAP. The so-called UAP markings are simply variations in the lake surface disruptions due to things like a forward motion velocity and wave interference around the UAP body. Exciting a liquids surface using vibrations or pressure waves has long been known and I will provide a few references here. It makes for pretty high-contrast photos. I note that some investigators have considered that part of this Costa Rica UAP was submerged as if entering or leaving the water. However those discussions don’t mention surface disruptions caused by a UAPs propulsion field and still presume a 638 ft UAP on or near the lake surface.


    It may be that the UAP detected the mapping plane and began moving. That could also explain the sharply defined rim of the surface disruptions (what appears to be the rim of a 638 ft disc). i.e. The surface excitation pattern had limited time to reach larger lateral extent. An article seen on the web attempts to explain the UAP as a boat wake however there are no shadows of the boat and it is doubtful a boat would leave a “wake” completely surrounding the boat. Further there are no other “boats”

Reference Links:

1) Journal of Scientific Exploration, Vol 3 No 2, Richard Haines and Jacques Vallee, pp 113-131.  

2) Article from the “Costa Rica Star”   

3) "Determinants of Faraday Wave-Patterns in Water Samples Oscillated Vertically at a Range of Frequencies

from 50-200 Hz". This is an excellent paper wherein acoustic energy excites a water surface from underneath and is photographed from above with high contrast lighting. This paper can be downloaded for free. I note that the authors recorded the timewise buildup and decay of the patterns and indeed at the beginning a sharply defined expanding “rim” can be seen

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