I dive, although down to at most 40m & I've no issue in diving in watches such as Rolex Submariner, Omega SMP, Breitling Steelfish/Superocean/SuperAvenger as well as others, but I also wear a dive computer of some description .. the only time I may opt for a Seiko (if not already on my wrist prior to a dive) is when drift diving in the UK .. dings/dents/scratches are par for the course .. getting moisture inside would be a nightmare, so always invest in a service prior to diving if concerned or if one has not been serviced for a while.