Also a
competitive swimming term. If someone is swimming too slow in practice but will not yield to endless tapping of their feet by a
frustrated swimmer behind them, this person would probably be
"deep sixed."
To deep six someone grab one of their ankles with one hand and pull hard backwards and down. As the victim passes underneath you take your other hand you push their head under and swim over them. Very effective if you know what you're doing, as there really is no defense for this if it is done correctly.