This is the reported naval ensign of Bolivia, created in 1966:
In the canton, you can see national flag of Bolivia; part of its symbolism was briefly addressed in another post. The blue color represents the sea, the nine stars represents the current nine departments of Bolivia. The tenth star, bigger and prominent, is the most dramatic part of the flag: it represents the lost Litoral department (that contained all Bolivian former sea coast) and, at the same time, the hope to once again have a sea access.
Although Bolivia doesn't have, currently, an oceanic fleet, the ensign is commonly saw in Lake Titicaca (the biggest South American lake) and many large rivers.
A variant flag found on photographs is the following:
The colorful checks is a representation of the Wiphala, a flag used by the native Aymara people and, since 2009, a national symbol of Bolivia. Its status is uncertain to me; any additional information is gladly received.
Comments are welcome!