"Turn turtle" is a term typically used to describe a vehicle or boat capsizing and flipping upside down in the water. However, there are several other synonyms that can be used to describe this phenomenon. These include "capsize," "overturn," "upend," "flip over," "invert," and "upset." Each of these words can be used to convey the same basic idea of something turning over completely. Whether you're talking about a small dinghy or a large ship, these synonyms can help you describe the experience of something going from right-side up to upside down in a matter of seconds.