Correct sentence: Fishing boats drag big nets through the water and scoop up lots of fish at once.
Why this is correct (easy steps):
- Subject and verbs match: "Fishing boats" is plural, so the verbs "drag" and "scoop" are also plural — that is correct.
- "In one go" is slang. "At once" or "all at once" sounds clearer for writing, so we changed it to "at once."
- "Lots of fish" is fine for talking. If you want a more formal word you can use "many fish."
Other simple versions you might like:
- Fishing boats tow big nets and catch many fish.
- Fishing boats pull big nets through the water and catch lots of fish at once.
Short note: Your original sentence was mostly correct. I just made the ending a little clearer by changing "in one go" to "at once." Great job!