1. I'm exhausted. 2. I'm dead tired. 3. I'm pooped. 4. I'm spent. 5. I'm beat. 6. I'm running on fumes. / I'm running on empty. 7. I can hardly keep my eyes open. 8. I'm off to bed. 9. I'm gonna hit the sack. (hit the sack = go to bed) 10. It's bedtime for me.
Because the fastest submerged objects (excluding missiles) in the world are all top secret military vessels it is hard to get reliable data on this subject. The fastest speed being claimed by any government out there however, was achieved by the Soviet K-162 in 1969. It allegedly reached speeds of up to 44.7 knots on trials which is already about 15 knots above any verified record.