In my travels throughout Central America, (Mexico to Panama and in between) the most common endemic submerged and semi aquatic plants I've seen include Hydrocotyl, Vallisneria, Arium Sword Plants (many bog and semi aquatic), Sagiterria and Nymphea waterlilies.
Floaters like Salvinia, water lettuce and water Hyacinth are also everywhere.
The various species and variants differ from country to country, and I admit I can't tell one from the other, but many genera are common from the southern US to Argentina.
And many Asian species have invaded and taken over, here in Panama.

Arium and Hydrocotyl above
Val below, and invasive Hydrilla in my sump below

Hyacinth in Lake Gatun, below collecting plants in Gatun

Hydrocotyl from Gatun

And found from the sea shore, in lakes and rivers the always present mangrove
