Pay attention to phantom cars, ox carts while taking a bend...
I know, landscape is fascinating, road in Tana-Toamasina route is superb but curvy. Even in daylights, other "drivers" may surprise you. Be it ghost cars or ox carts.
Don't drive so fast, especially when taking bends since truck drivers are sometimes sleeping (yes!). They don't sound their horns. And while driving at night, some just forget to put on lights. Well, as for carts, you just have to know that they are driven in same roads as yours.
Toamasina and East coast in general offer this vision of luxuriant fauna, lush flora, with much waters.
Pay attention to what guides, locals, pousse-pousse men tell you about waters.
Don't swim "off the beaten track" since rivers and soft waters are home of saurians (crocodiles of all kinds) while sea outside coral reef abounds in sharks... If there is a fady (an interdict) on a pound, be sure it is more for safety purpose than related to local beliefs !