Conclusion:
Faster Sailing-Time: ...... 120 km/day.
Avg Sailing-Time: .......... 100 km/day.
Slower Sailing-Time: ....... 80 km/day.
Avg Sailing-Time: .......... 100 km/day.
Slower Sailing-Time: ....... 80 km/day.
Link:
169-217 km per day (Avg 195 km), from that Table (above.) This is probably 'wrong' - exceedingly fast in nearly all likelihoods. While particular shorter routes may have run fast, longer routes almost certainly did not. Rome (Ostia) to Alexandria was a longer route.
Galba's accession was known in Alexandria by 6 July, within 27 days of Nero's death on 9 June AD 68
Rome to Ostia took 6-9hrs, waiting on a vessel might be another 6-12 hrs, ergo 1 Day. Ostia to Alexandria in 26 Days sounds exactly right (100 km/day).
Another site stated:
16-21 days .... Alexandria to Ostia
9-10 days ...... Alexandria to Antioch
9-10 days ...... Alexandria to Antioch
Too fast/short @ 20 days, here. Ostia-Alexandria was 2,615 km. so probably 22 days was a reasonable minimum (120 km/day) but faster than avarage.
Link:
Galba's death known in 27 days (C.I.G. 4957), whereas news of Pertinax's accession (on 1st January) took 65 (B.G.U. 646), while his death on 28th March had not reached the Fay'um 52 days later (B.G.U. 46). Nero's death known at Elephantine in 57 days (Griech. Ostr. 799).
News of Galba's death travelled 100 km/day; the fastest reasonable time would have been 120 km/day.
The very slowest boat from Ostia-Alexandria was 41 km/day - highly improbable, I think. Regular delay, somewhere (totaling +30 days), and 70-80 km/day was more plausible. It seems official news traveled from Ostia to Alexandria in ~45 days. With poor winds, news travelled 60 km/day by Sailing-Time.
If Alexandria to Fayum was 240 km, the upriver Nile sailing-speed was +2 days.
If Fayum to Elephantine was 800 km, the upriver Nile sailing speed was 118 km/day.
The Alexandria-Elephantine upriver Nile sail took +8 days at least; Diodorus Siculus says 10 days.
Alexandria-Bethlehem in 16 days, Sulpic. Dial. 1.8.1.
'600 km in 16 days' is 118 km/day sailing-speed.
Link:
However, in the Roman period a journey from Alexandria (which is located in the western extremes of the Nile delta, ca. 250 km west of Migdol/Pelusium when following the shoreline) to Palestine by boat could take between five and seven days, cf. Harold W. Hoehner, Herod Antipas (Grand Rapids: Zondervan 1980), 36 note 5.
Pelusium to Gaza was only about a two-day journey by boat.
If Pelusium-Alexandria was 295 km, the sail-time should be 2.5 days at least (assume '3 days' minimum).