Provided dataset Cameroon water bodies does not have the CRS defined.

sf::st_crs(mapMCDA::mapMCDA_datasets()$water_bodies)
#> Coordinate Reference System:
#>   User input: Undefined geographic SRS 
#>   wkt:
#> GEOGCRS["Undefined geographic SRS",
#>     DATUM["unknown",
#>         ELLIPSOID["unknown",6378137,298.257223563,
#>             LENGTHUNIT["metre",1,
#>                 ID["EPSG",9001]]]],
#>     PRIMEM["Greenwich",0,
#>         ANGLEUNIT["degree",0.0174532925199433,
#>             ID["EPSG",9122]]],
#>     CS[ellipsoidal,2],
#>         AXIS["latitude",north,
#>             ORDER[1],
#>             ANGLEUNIT["degree",0.0174532925199433,
#>                 ID["EPSG",9122]]],
#>         AXIS["longitude",east,
#>             ORDER[2],
#>             ANGLEUNIT["degree",0.0174532925199433,
#>                 ID["EPSG",9122]]]]

^{Created on 2024-01-29 with reprex v2.1.0}

Re-save the packaged object with CRS WGS 84 (EPSG 4326), as for the other packaged layers (checked).