Is the word ondas the same in Brazilian and European Portuguese?

Yes

The only difference between the word "ondas" in Brazilian and Continental Portuguese is pronunciation. In Brazilian Portuguese, the vowels are generally more open, and the rhythm is syllable-timed, meaning the "a" in "ondas" is clearly articulated. In Continental Portuguese, the rhythm is stress-timed, which causes unstressed vowels to be reduced or almost swallowed; consequently, the "a" in "ondas" is much shorter and more closed, sometimes sounding nearly silent to a non-native ear.

Brazilian Portuguese

1. As ondas do mar estavam gigantes hoje. (The sea waves were huge today.)
2. Ela tem ondas naturais no cabelo. (She has natural waves in her hair.)
3. Uma onda de calor está chegando ao Brasil. (A heat wave is arriving in Brazil.)
4. O rádio captou ondas de sinal bem fracas. (The radio caught very weak signal waves.)
5. Eu adoro surfar nessas ondas. (I love surfing these waves.)

Portuguese (Portugal)

1. As ondas do mar estão a ficar gigantes hoje. (The sea waves are getting huge today.)
2. Ela tem ondas naturais no cabelo. (She has natural/her natural waves in her hair.)
3. Uma onda de calor aproxima-se de Portugal. (A heat wave is approaching Portugal.)
4. O rádio captou ondas de sinal muito fracas. (The radio caught very weak signal waves.)
5. Gosto de ver as ondas a quebrar na areia. (I like to see the waves breaking on the sand.)