The only mention of a rowing chant that I've found is in the work 'Sar Orain: Three Gaelic Poems', which makes mention of rowing chants and even defines which oarsman makes the chant and when.
An excerpt from that work...
"Brosnackadh Iomraidh
The boat has to be rowed out from the shore, before the sail is hoisted , to be clear of rocks and to catch the wind. lonad seòlaidh is the place where ' sailing,' as contrasted with ' rowing,' begins.
Metre
The couplet consists of a long line of eight syllables, and a short line of four syllables, both ending on a dissyllable, and the couplets rhyme.
This is Sneadhbhairdne, 2{S-+4:^f+' . In this section, however, the long lines of the quatrains also rhyme, except in the first. As dealbhach occurs again in the second quatrain, the first line may have been wrongly transcribed . The emendation dhionach is suggested by "An Duanag Ullamh," two quatrains of which are given below, from Rel. Celt. II. Compare with the "Birlinn" for metre and style.
Loingis leathann laidir luchdmhor
Dealbhach dionach,
Sleamhuinn sliosreidh roluath ràmhach
Dairchruaidh direach.
Togbhar leo na gealchroinn chorrach
Suas le 'nlonaibh, '' ''l^ ^'*^ ^^^
B' iomdha ball teann bhiadh ga n deanamh
Nam dhuit seoladh.
(This poem was composed by the "Mull bard," before 1558, and may have been known to MacMhaighstir Alasdair. See note on the poem in "Bàrdachd")."