Belize in May - pica pica?

We are traveling to Ambergris Caye next month. We have heard that 'around
this time of year that divers may come in contact with pica pica and develop
an itchy rash similar to chicken pox that can last up to 10 days. Pica pica
is thought to be spherical thimble jellyfish blooms that contain millions of
juvenile jellyfish that can't be seen with the naked eye and can give people
a rash because of the medusa (tentacle-like structures) they have that
contain nematocysts (microscopic and poisonous). They are activated by
touch, leaving the person with the pica pica rash. The traditional remedy is
to put vinegar or ammonia on the affected area.'

What preventative measures work effectively? Applying baby oil or vaseline
on the skin before diving?

Thank you,

Phil