Sweeeet! I've always really liked the Sea Hawk. The styling of the knife has many visual similarities to the Bowie, giving it such a classic American style. IIRC weren't they first made in 1971 or 1972 and one of the first dive knives to use both a full tang and PM stainless steel in the same package?
I have cobalt alloy knives from David Boye, Kit Carson and Rob Simonich (I sure miss Kit and Rob) and a few beta phase Ti alloy pieces from Mission and custom makers that won't "rust" because there's no steel to rust.
Most commercial dive knives are made with the focus on corrosion resistance over other characteristics and the search for good cutting properties that won't rust has lead to nice innovations.
I agree the primary goal for dive knives now is corrosion resistance ahead of everything else...it has yielded some cool innovations, but in other areas I think it has resulted in trade-offs. I honestly always felt the cobalt alloy steels were better than the later nitrogen work-hardened steels in terms of overall performance.
I have a few knives in the Cobalt-Vanadium Bohler N690 stainless and even though it isn't mentioned very much, it's overall performance is outstanding. It takes a very aggressive edge and holds it like VG-10, seems to be tougher with superior chip resistance, has outstanding corrosion resistance, and is easy to sharpen. It's also more economical than many of the PM super steels.
Spyderco's H1 is really awesome steel, but I have always been underwhelmed by the edge-holding of plain-edged H1 blades, which I don't find to be much better than 440A-B. However, a friend of mine has a fully serrated Tasman Salt in H1 and it holds an edge better than high-hardness VG-10. My guess is that the grinding of the serrations themselves caused the work hardening, and this may have been slightly furthered by the constant sharpening over a decade?
All-in-all, I think there are some situations where with plain-edged dive knives that the balanced performance and cost efficiency of a cobalt stainless like N690 is more desirable than a steel where all other properties take a back seat to corrosion resistance.