Shadowrun mechanics IMO make it tougher to go from character concept to effective build than it is to make an effective build and then build a character around it.
If you have a concept, don't expect that everything is going to be represented well in active skills/dicepools. They can be (depending on the concept), but don't count on it or fret about it.
Characterization on paper can come in other meaningful ways:
Knowledge Skills -
These represent a log of professional, background, interest, etc. pieces of your character that you can represent on your character sheet without having to compromise effective shadowrun active skills. These are the most freeform parts of character generation, and I think folks should take advantage of that and make fun and unique knowledge skills for their characters (and GMs should be more partial to more narrow skills or more generic ones).
Contacts -
Here is a another way to show more about your character concept without altering your main dicepools. You can express a lot of a character concept through the people that are important to your shadowrunning career, and flesh out more about your character in relating to these people.
Qualities -
Here are other ways to demonstrate parts of concepts, particularly negative qualities.
Adept Powers/Spells/Tradition/CFs/etc -
These are further options to demonstrate character concept, allowing background/history/lifestory to be shown on a sheet.
Unique Gear (interesting foci, cool car, named deck, etc.) -
These are other ways to bring more of a character concept to your sheet without altering functionality.
For your example (dwarf that worked underwater construction), the character doesn't necessarily need to be skewed towards dicepools in swimming, diving, nautical engineering, nautical piloting, survival, etc. It can, but if you can't also make a character that is good at shadowrunning, than it is probably not going to be a fun concept.
Instead, the character may have professional knowledge skills related to underwater construction (ex. architecture [underwater]), Marine Geography, Sea Legends, etc.), a dockworker contact, Flashbacks quality to almost drowning, specialize in summoning water spirits, owns a boat or water drone, etc AND also have the stats/skills of the specialty they bring to their team.