Is it okay for my wife that is 20+ weeks pregnant to go snorkelling? Anyone have good advise?

No, what if met with strong currents or stung by jellyfish? Better be safe than sorry

To be on the safe side (and for your peace of mind) best to check with your gynae.

Nah.. don't try adventurous activities at this moment

Get advise from gynae

Consult your gynae

Is good to avoid

Not advisable.

Nah. Do avoid

Better not to

Better not