I have found the Tusa Imprex FK-210 a great knife for all my diving needs, and it is also a great bargain that offers a very good performance/price ratio.
The knife has a 5 3/8” long 420 Stainless Steel blade. One side of the blade has a smooth and a very very sharp edge. The other side has a serrated edge (also quite sharp) and a line cutter. At the end of the handle there’s a hammer knob that can be used for various purposes.

The knife comes with a nice looking plastic sheath, that has a quick release button and 2 adjustable rubber straps for the leg. The construction of the sheath feels solid and the knife feels quite secure inside the sheath. The rubber bands are also comfortable to adjust, to wear and to strap on the leg.

The blade edge is so sharp that I’ve succeeded to shave off some of my hand hair with it (I did just to try how sharp it is), the point also feels pretty sharp (in case you ever need to stab something in the water). The serrated edge can be useful for cutting ropes, nets or whatever you need to cut. The wire cutter, in addition to cutting wire, can also be used in case that you need to rescue someone and you need to quickly cut his wetsuit in order to to perform CPR. The hammer thingy on the back of the handle can be used as a hammer or in order to create noise in the water by banging it on the tank (to attract attention).

Another great feature of the knife is that it can be easily disassembled for cleaning and washing after a dive. It is not a secret the Stainless Steel knifes require some TLC in order to prevent rusting (unlike titanium knifes that don’t rust at all, but are more expensive). When you unscrew the handle knob, you can disassemble the screwing inside, and get the entire blade separated from the handle (see pictures).

The only disadvantage that I’ve found in this knives that the screwing that hold the blade attached to the handle is made of plastic instead of metal. It seems to hold the blade in a quite solid manner, but something about plastic just feels too cheap to me – I just hope that it has no tendency to break.

Tusa also manufactures another version of this knife, the Imprex FK-220. the only difference between the FK-210 and the FK-220, is that the 220 has a blunt blade, which can be useful to some people, but I personally don’t like it so much.

This is the link to the manufacturer’s website.