GG5

https://ejje.weblio.jp/content/平底舟
斎藤和英大辞典での「平底舟」の英訳
平底舟
読み方 ひらぞこぶね

barge, punt
https://www.ldoceonline.com/dictionary/japanese-english/平底船
平底船（ひらぞこぶね）
plus:
平底船の竿 [名]
‣ barge pole → See English-Japanese Dictionary
平底船の船頭 [名]
‣ bargeman 米, bargee 英 → See English-Japanese Dictionary
平底船員 [名]
‣ bargeman 米, bargee 英 


Plot thickens:
https://www.oceandictionary.jp/subject_1/ej-bunya/vessel-ej.html
dory: 平底船(ひらぞこぶね)(→ pontoon, sharpie).

Only furigana is スカウ (scow) and one カルバス(?)
https://furigana.info/w/平底船
Reading ひらぞこ probably obvious, and thus never gets furigana

Reverso: "flatboat" "barge"
https://context.reverso.net/translation/japanese-english/平底船

平底	10964	  
平底の	3319	  
平底の歩きやすい	1213	  
平底の歩き	1213	  
平底の歩きやすい靴	1211	  
平底舟	1165	  
平底船	818	

yourei:
平底舟 31
平底船 178

We only have ひらぞこ for 平底 itself, so missing the rendaku here would be particularly odd.  Looks like it's just a mistake.
A google search for "ひらそこぶね" is a good google search to see who's rebroadcasting jmdictdb content, like the intentional dictionary misspellings of old.

I didn't know a "flatboat" was a thing, but it seems particularly common on reverso.  oceandictionary also offers "dory", xreffed to "pontoon" and "sharpie", all three of which google tells me are kinds of flat-bottomed boat.  None of these are used on reverso, but that's hardly definitive.  Still, they seem more useful as E->J glosses than J->E glosses (they seem to represent very specific western boats).

@@ -6,0 +7,3 @@
+<k_ele>
+<keb>平底舟</keb>
+</k_ele>
@@ -8 +11 @@
-<reb>ひらそこぶね</reb>
+<reb>ひらぞこぶね</reb>
@@ -12,0 +16,2 @@
+<gloss>flatboat</gloss>
+<gloss>barge</gloss>