The oce package has a world coastline file that is visibly crude on a scale suitable for continental-shelf work. At the cost of about 1 Mbyte of storage, a candidate for a replacement is a 1:10million scale version downloaded from naturalearthdata.com (full link below).
As illustrated below with plots near two oceanographic centres, this candidate provides noticeably more detail.
The code to make the graph is below. Readers wishing to reproduce this will need to download the coastline file named in line 2, from the naturalearthdata website (download link http://www.naturalearthdata.com/http//www.naturalearthdata.com/download/10m/cultural/ne_10m_admin_0_countries.zip).
NB. The link at the end of the previous paragraph downloads a 8.4 Mbyte data file that becomes a 3.0 Mbyte file in R format, which is to be compared with the 1.8 Mbyte file for the existing coastline. The existing coastline has 406694 points, while the 1:10m version has 552670 points (i.e. 30% more points); the mismatch between data-size ratio and file-size ratio perhaps has something to do with compression.
library(oce) d <- read.oce("ne_10m_admin_0_countries.shp") ## Two panels illustrate two oceanographic centres. par(mfrow=c(1,2)) ## Left panel: Halifax NS, with grey for existing ## world coastline and blue for the 1:10m version ## under consideration. plot(coastlineWorld, clon=-63.60, clat=44.65, span=200) lines(d[['longitude']], d[['latitude']], col='blue', lwd=1.4) ## As left panel, but for Woods Hole MA. plot(coastlineWorld, clon=-70.70, clat=41.65, span=200) lines(d[['longitude']], d[['latitude']], col='blue', lwd=1.4)