• Regarding any breath-holding activities in water, it is imperative to both have a properly trained spotter / buddy, as well as to be properly trained yourself.  
• Many agencies will be able to train and certify you in proper breathhold safety protocols, including AIDA, PADI and SSI and it is well worth the investment in yourself.
• Ensure that you are healthy and fit before any sort of strenuous exertion and validate with a medical doctor that monofin swimming is something that you are able to do, safely.
• Additionally with monofins, because your feet are essentially bound together it is crucial that you be both buoyant on the surface and are also able to tread water with just your arms for an indefinite period of time.
• Lastly, do not let children of youth swim with a monofin unsupervised.
• Have fun, swim / dive safe and enjoy your Lunocet!

Regarding Sharks and other large predators:

• It is never a wise practice to enter murky or low-visibility waters with top apex predators.  
• Additionally, even in very clear water, species such as Great Whites, Bull Sharks and Tiger sharks have been known to occasionally mistake humans for prey.  As such, swimming in waters with these beautiful, magnificent creatures should be avoided.

Picture of the owner swimming with over a dozen large (6'-8') reef sharks in Roatan, Honduras at 80' feet deep, clear water on a reef, while respecting their space.