Berceuse da onda is a more harmonically complex work that evokes the rhythmic swaying of waves. It is distinguished by its rolling, undulating left-hand figures that create a hypnotic effect.
The primary challenge is to sustain a continuous, flowing wave-like motion without allowing the rhythm to become stagnant.
Comparable difficulty and character — good candidates for what to learn next.
Berceuse da onda (Op.57) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Berceuse da onda (Op.57) lasts about 4 minutes.
Berceuse da onda (Op.57) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include As estrelas by Oscar Lorenzo Fernández, Boneca Yayá by Oscar Lorenzo Fernández, Berceuse da Boneca Triste by Oscar Lorenzo Fernández — see the full similar-pieces list on this page.