Cluin,
When in southern and especially equatorial waters total body coverage from the sun is a good practice from burn. When anchored total sun coverage is also the safe way to go especially if the wind ceases and the air born critters locate you. Although long before sun blocker's we did sail and swim sans clothes but the painful memories outweigh the pleasure and excitement of yesteryears total abandon. Coverage from the sun and water slime are the order of today.
I have heard of these critters you mention but experienced none first hand. There are many other nightmare possibilities thru out CA & SA. Bot flies come to mind first. You can't know just when you will swallow one. In the states as they mature they crawl up toward the trachea and upon sensing light bore their way out at the throat but in the intense southern light they bore straight out thru the stomach or intestine. When they appear you tie their head to a stick and wind up an inch or so of their length each day until the entire worm is removed. Very messy and smelly as some reach three feet in length taking weeks or months to extract. If the wound is not covered during this time there is great risk of attracting additional family members.
Deep in the jungle and in remote coves I've seen many large animals afflicted with parasites. On one trip along costal Columbia I anchored several weeks trying to tame by hand feeding a large cat in order to try aid her. Was very sad to finally fail and leave her behind tame but unaided. A very profound experience for both her and I.
Be it in the outback of SA or Africa checking oneself often for parasites is the rule. Some nights after river crossings just removing suckers takes till dawn. Their marks last for years.
Most parasites rarely kill their host is the only rationalization on the bright side. Diver