You might try clipping that ocean shapefile with a ±90 ±180 bounding box. Some open source tools don’t like polys that are outside of the normal extents (eg: part of that polygon might be north of 90°). Hoping to fix that in the data eventually, sorry for the inconvenience!
Nathaniel thanks so much for your help!
I have to admit I’m really a “newbie” with QGIS and I’m not totally sure how to use a bounding box. Is it a feature of QGIS itself or an alteration I need to make in another piece of software?
You should file a bug for the QGIS software.
If a software crashes when presented with bad data, it’s always a bug. Software should never crash, it should present an error message or otherwise deal with bad data.
Also, there’s the chance that they fix the bug and that future QGIS version could load the file as-is, without hickup.