Occasionally, a vocal strain more sonorous than the generality informed the listener that some boastful bass was in blue water, or in the hunting field, or with the reindeer, or on the mountain, or among the heather; but the Marshal of the Marshalsea knew better, and had got him hard and fast. The preceding passage is from Dicken's Little Dorrit chapter 32.What does the term "boastful bass in blue water" mean in the above context.What does the term " had git him hard and fast " mean in the following sentence.

This passage is from chapter 32 of Little Dorrit by Charles Dickens, with the phrases I’m curious about set in bold:

Occasionally, a vocal strain more sonorous than the generality informed the listener that some boastful bass was in blue water, or in the hunting field, or with the reindeer, or on the mountain, or among the heather; but the Marshal of the Marshalsea knew better, and had got him hard and fast.

1. What does boastful bass in blue water mean here?

2. What does had got him hard and fast mean here?