There are three* Phrygian words related to water and one of them is ΒΕΔΥ. The account for this word, comes from Clement of Alexandria who lived in the 2nd century AD and got exposed to the neo-Phrygian language. Immediately one would read the word as bedu which doesn't sound convicing at all to my ears. It doesn't take much time to understand that what Clemens heard from the Phrygians was wedy or vedy and not what reads in the latin alphabet as bedu. Remember that the Greek Β (beta) was not always equal to the Latin /b/. After some point, /b/ became a /v/, while /w/ (Ϝ - digamma), when not dropped, turned either to /v/ or U+vowel. The later is attested in both Phrygian and Greek, however we have no clear evidence that Phrygian /b/ turned to a /v/. In any case, we should seriously consider reading ΒΕΔΥ with a medieval Greek β, rather an archaic one. Besides, ΒΕΔΥ should have the same root as all other Indo-European words for water, that is to say *wed-o-/*wódr̥. There is not a single Indo-European language where the word for water starts with a B. Meanwhile, J. Pokornys Illyrian gw-> b- phonetic mutation theory, seems very unlikely. Some Indo-European examples on water listed below.

English: wæter
Hittite: watar
Luwian: wārsa
O.C.S: voda
Proto-Greek: *wydor (later ydor)
Cap. Greek: vuδokko
Tocharian: war
Ossetian: wydr
Lithuanian: vanduõ
Old Prussian: wundan
Old Norse: vatn
High German: wazzar
Umbrian: utor (*wutor ?)

* The other two words for water are ydor and akala, the later being the only one directly attested on inscriptions.