READ OUT LOUD. Choose which marked text you prefer to practice with - macrons or accent marks - and read the text out loud until you feel comfortable and confident. Then, try reading the unmarked text at the bottom. It should be easy for you after practicing with the marked texts. :-)
MACRONS. Here is the text with macrons:
In ūnum convēnerant fluviī, mare ut accūsārent, quod sē, simulatque eius intrāssent aquās, dulcēs quamvīs essent et potuī aptī, falsōs et ad bibendum redderet inūtilēs. Quae mare cum audiisset, aegrē ferēns innoxium sē culpārī: "Nōlīte (inquit) aquās intrāre posteā meās, nē corrumpāminī sale."
ACCENT MARKS. Here is the text with ecclesiastical accents, plus some color-coding for the words of three or more syllables (blue: penultimate stress; red: antepenultimate stress):
In unum convénerant flúvii, mare ut accusárent, quod se, simulátque eius intrássent aquas, dulces quamvis essent et pótui apti, falsos et ad bibéndum rédderet inútiles. Quae mare cum audiísset, aegre ferens innóxium se culpári: "Nolíte (inquit) aquas intráre póstea meas, ne corrumpámini sale."
UNMARKED TEXT. Here is the unmarked text - after practicing with the marked text that you prefer, you should not have any trouble with the unmarked text:
In unum convenerant
fluvii,
mare ut accusarent,
quod
se,
simulatque
eius intrassent aquas,
dulces quamvis essent
et potui apti,
falsos
et ad bibendum redderet inutiles.
Quae
mare cum audiisset,
aegre ferens
innoxium se culpari:
"Nolite (inquit)
aquas intrare postea meas,
ne corrumpamini sale."
IMAGE. Here is an illustration for the story (image source) showing a river falling into the sea:
